How can I make cushions for my wicker chairs?

Linda: maybe these will help

https://www.doityourself.com/stry/how-to-make-wicker-furniture-cushions

https://www.ehow.com/how_6145969_make-outdoor-cushions-wicker-furniture.html

If you were starting from scratch. . . that is did not have the cushion nor the cover, then it would probably be as costly to make as to buy new. Foam is expensive, and so is fabric. If you can find old cushions, then it is much easier to make just the covers. The fabric on these chairs was faded, they were professionally made but I did not want to go to that trouble, so I got 4 fleece blanks for $3 each and simply basted them over the cushions. The cushions are what is important.

Foam that is suitable for chair cushions (as opposed to toss or decor cushion foam) needs to be adequately thick and dense to support the weight of someone sitting on it.

Emily is right that this type of foam is not cheap by any means. Adding in the cost of fabric, and it may very well be more cost effective to purchase new ready-made cushions.