"Beyond Salvage" is the original title of this HOW-TO video from the Chez Maison media team (Jim Clarken & Isabella Codd.)
It is an upcycling project that we had some wood-working help on. The cushion is designed to use up a shirt from the second-hand store but you can use curtain fabric that you want to re-purpose. The main skill that I wanted to pass on, was the making of the template of the chair seat into a useable working paper-pattern. Particularly useful if you had more than one chair of the same style/size. You can use the same pattern over and over, perhaps with some contrast or variation of fabric/colour on each. (Especially if you have a 'wardrobe' of shirts to use.)