I had an assistant some years ago who drove me crazy (among other reasons) by spending endless hours cutting out prepared perfect pieces for crafts. She missed the whole point of preschool crafts!
Crafts are not, not, NOT about making a perfect copy of a perfect <feh>Martha Stewart model. There is no need for a parent/caregiver to take the item out of the child's hands so it "looks right". It's not about that. It is, as any preschool educator worth their title can tell you about the process, NOT the practice!
Craft activities can teach children important skills, like using a scissors. They can help them can practice hand-eye coordination. They let them play with colors. They let them use their imaginations, something that kids seldom get a chance to do on a regular basis nowadays. Above all they should be FUN!
As are these spiders on a web:
I did have to cut slots around the edges of the plates in advance. Using a hole puncher way on the edge worked perfectly.
The kids chose their yarn and we taped the end to the back. Then they got to wind it from slot to slot however they pleased. One or two kids needed to be shown the basics, but then they did fine on their own.
The fun is in making it--all by yourself!