Somewhere in the 1400s, rectangular construction gave way to a new generation of highly-tailored styles. These garments don't have a single straight line in them! Many are fully lined or have cuffs, collars, and other structured elements.
As with anything, there is a learning curve -- and there are common mistakes that you can learn to avoid. I made a series of videos on these. I will add more videos to the "tailoring topics" whenever I happen to work on projects that highlight additional techniques.
How to convert the sleeve seam into a laced or buttoned opening.
Direct link: https://youtu.be/hnVlJeLNf4g
Successfully attach an inset sleeve (and ease in the curved shoulder).
Direct link: https://youtu.be/oYzMuDglZPY
Lining the body -- without sewing yourself into a corner!
Direct link: https://youtu.be/SUW7WHkQb8g
I found this grey dress at a SCA "yard sale" for $10 -- a steal! Many of the seams were coming apart, especially around the armholes, and it was in the loose early-14th century style rather than my persona's end-of-the-century style. This was a good project to illustrate several easy alterations:
Stabilize seams by re-sewing with deeper seam allowances
Take in fullness at long seams
Split a seam and convert it to a laced opening
Add a new (center front) seam
Cut a new neckline and finish with bias tape
Make the lower sleeves tighter, not shorter (preserves ease of motion)
Shorten the hem
I remembered to grab video of some of those steps, and I am slowly editing them for YouTube. Find them in the Shorts section of our YouTube channel: https://www.youtube.com/@ravenswatchfarm/shorts
Note: If your browser settings won't let you see the YouTube videos as embedded, clickable elements, you can click this link to go to the playlist with all these videos (and more!): https://youtube.com/playlist?list=PLl7yvdDBVO_ByTpqkb6b8WIyIzAPBzcZh