Now we get to really start putting this thing together! On both the lining and the outer fabric, sew the shoulder seams. Make sure you've got the wraps on the correct shoulder, because unpicking and resewing is no fun. Press your seams. Whenever you press a seam you want to press it on one side, then the other side, then press it open. Yes, it's tedious AF. But it really helps the thread to sink in better. Trim the seam allowance of the shoulder lining to be smaller (not your outer fabric). This is known as grading, where you make your seam allowances different widths to avoid having too many stacked together, which might show through as a bump or ridge on the outside. Optional Couture Tip: If you have a very fine wool where pressing open the seam allowance is going to leave a ridge on the outside of the the fabric just where your fabric ends, you can either press it on the edge of your ironing board, or pop a bit of cardstock in between the allowance and the main fabric to try and avoid that. Optional Couture Step: I catch-stitched a bit of twill tape into the shoulder seam of the wool layer to help the shoulder avoid stretching over time. I would have preferred a narrower tape, but 1/2" was the smallest I could find in my stash. (I didn't do this to the polyester since that would have added too much bulk, and also poly is less likely to stretch). Now it's time to sew in the sleeves! Woo this feels like such forward progress! Note that while your seam allowances are the same length, the actual edges of the fabric will not be the same length because the sleeve at the shoulder is such a dramatic curve (and the wider your seam allowance is the more apparent this will be). Whenever you are dealing with matching a curved seam to a straight seam, or an outer curve to an inner curve (e.g. a princess seam), you want to clip the piece that needs to stretch and notch the piece that needs to be smaller. (I find this more intuitive than remembering which one you do to outer vs inner curves. The key is if you find yourself trying to smoosh a seam allowance in and it's getting wavy, clearly its too big and needs notches removed. If you are trying to stretch one out and it's not big enough, it needs to be clipped to allow it to stretch). Here I'm stretching out the straight side with my hand so you can see my clips, but those are just snips directly into the seam allowance (not little triangles cut out like the other side). Sew both sleeves in on both the outer fabric and the lining! Again, checking very carefully to make sure you've got your left and right sides correct, or it will hang weird and you'll have to redo work. Press your seams. It is tricky to press a curved seam on a flat surface so a tailor's ham is really helpful. If you don't have one, wad up a towel and iron over that.