Hurray, we're finally sewing! Today we're going to sew the jacket front darts, attach the side panel and then insert the welts as the first stage of creating your gorgeous welt pockets. (Throughout this post I talk about sewing one pocket but obviously you'll want to repeat the process for both sides of your jacket.)
Anyway, first up we're going to prepare the jacket front. Sew the darts in the jacket fronts. These are narrow darts and you should ignore the dot that's near the base - that's nothing to do with the dart. Securely tie the thread ends and press the dart over towards the side seam.
Now you've sewn the dart, you should find that the two raw edges of the slit running from the base of the dart to the side seam are now the same length. Match them up, and using a wide stitch, zigzag over them to close up the slit. They shouldn't overlap, just abut. 
Next take your jacket side panels and match them to the jacket fronts; the notch on the side panel should meet the end of the zigzagged slit. Stitch them with a 15mm (5/8 inch) seam allowance, and press them open. The next step is to apply your pocket area interfacing; it should cover the area between the two dots, sitting over the zigzagged slit and over the side seam. Embarrassingly, I forgot to do this myself whilst sewing and photographing! (Do as I say not as I do ;) ) Once you've done this, you're ready to pick up your pocket pieces. 
Press your welt pieces in half lengthways with the wrong sides together. Baste down their lengths at 5mm (1/4 inch) from the folded edge. 
Match the pocket flap lining pieces to the pocket flap fabric pieces, right sides together, and stitch around the short ends and the bottom edge (between the curves), using a 15mm (5/8 inch) seam allowance. Trim the seam allowance down, ideally with a pair of pinking shears - if you have these you should trim close to the stitching around the curved corners as this will help them turn out smoothly. If you don't have pinking shears, clip little triangles into the seam allowance at the curves. 
Turn the flap the right way out, pushing out the curved corners. Press then baste the remaining raw edges together at 15mm (5/8 inch) in. 
Now we're going to check that the space we've marked for the pocket on the jacket itself is accurate. Lay your flap against the jacket, matching one end to the dot beside the base of the dart. Check whether the second dart (in the side panel) is sitting flush with the other end of the flap; if it's not, remove the tailor's tack and make a new one or some other mark where the flap does in fact end. These dots mark the pocket opening and you want that to match the width of your flap perfectly. 
You can see in the above photos that my flap was wider than the marked space (probably because I didn't use sufficient seam allowance when sewing my flap) so I ignored the right-hand tailor's tack and placed a pin to mark the correct endpoint of the flap.
Now set aside the flap and run lines of hand-basting directly up and down from your two flap endpoints. Don't machine baste as you want to be able to remove these easily and with minimal impact. Don't use chalk as you want to be able to see all this basting on both sides of the fabric. 
Now I'm really sorry to say that the next step was actually missed out from the first printing of instruction booklets for the printed Richmond pattern, so if you're referencing a printed booklet you might not find it. The diagrams and text are included on our Errata page but I'll explain everything below of course.
The zigzagged slit is going to become part of your pocket opening; run a line of basting stitches to extend the line from the slit up to where you've confirmed the flap will end. This line now represents your pocket opening. Mark two more lines of basting parallel to the slit-line at 5mm (1/4 inch) above and below, extending them 2–3cm (1 inch) past the vertical lines at each end. 
So you now have a nice little rectangular frame of basting lines to work with. Take one of your folded welts and place it (on the right side of the jacket) so that the line of basting on the welt lies directly over the upper line of basting on your marked rectangle, with the raw edges of the welt facing downwards. The welt will be longer than the pocket opening; position it so the excess at either end is roughly equal. 
Taking care that the welt doesn't shift out of place (if your fabric is very slippy, it might even be worth basting it in situ), stitch the welt to the jacket on top of the welt's existing line of stitching, starting and stopping between the lines marking the ends of the pocket (i.e. where the first and last pins are in the above photos). The ends of the welt will be free. 
To make way for the second welt, pin the raw edges of this first welt up and out of the way. 
Now pin the second welt in place along the bottom basting line. This time the raw edges will be pointing upwards. 
Repeat the process of stitching the welt in place between the vertical lines. Once stitched in place, the raw edges of the welt will meet in the middle like lips! I removed the pins from the first welt so you could see this but actually as you then have to pin back both welts there's no need to remove that first lot of pins. 
Keeping those welts pinned out of the way, you want to unpick the zigzag stitches holding the slit together. This becomes the main part of the pocket opening. Using a small pair of scissors and taking it slowly and carefully, extend the slit along the line of basting, stopping 5mm (1/4 inch) before you reach the endpoints (marked by the vertical lines). Now, at each end of the slit snip from the opening line into the corners of the basted rectangle, right up to the welt stitching, making a Y shaped cut. Be super careful not to cut beyond the rectangle as this will make your pocket opening too wide.
You can just about see the Y shape of the snips here.You can now remove all the pins and push your welts through to the wrong side of the jacket – you should be able to see the welt pocket taking shape! You can also now remove your basting.
(These pins are just holding the welts in place - the velvet was a little bouncy...)
We're going to stop there for today because phew, haven't we done rather a lot?! If this is your first time sewing welts, pat yourself on the back. Next: on Thursday 12th I'll be publishing the next post where we'll insert the pocket flap, and then the pocket bag.