My grandmother bought a dining table with these chairs at a garage sale:
If you're thinking they don't look that bad, you should have tried sitting on them :)
The foam was deteriorating, making for a rather uncomfortable seat.
Also, the fabric looked kinda gross up close.
Remove the old fabric (however many layers you find, :) and old foam with needle nose pliers.
Glue foam to base. If you want a rounded edge, just glue around edges and sort of fold it over as shown in the picture above.
There's the finished product!
I just re-did this entire dining room for my grandmother, and I'll be showing y'all the pictures soon! It was a lot of HARD WORK, and I'm SO excited it's almost ready to show off!