Cushion: Best of Both Whirls
There are no curves here. The spirals you see are made entirely from straight lines. You can make Best of Both Whirls from 1 large module or 4 small ones. Either way will give you exactly the same size so the back and front could be different.
We also have an afghan version of Best of Both Whirls.
Buy the cushion pattern using the link at the top of this page
or in Cushy Numbers - a book of 12 patterns