Wheels Within Wheels
Despite what your eyes may tell you, there are no curves here.
Wheels Within Wheels is a tessellation of pentagons with all sides equal. There are very few 5-sided shapes that can be fitted together to cover the surface without leaving gaps. This is one of them.
The afghan shown in the first photo consists of 90 identical pieces which are stitched together. The stitching is very easy because they are all in garter stitch and the edges are easy to match together. The afghan will lie flat without any blocking.
The instructions include some short cut ways to make some of the pieces, to reduce the amount of stitching.
These particular pentagons fit together in a very limited number of ways. One of the pictures shows variations you could make and the pattern tells you how to go about making those variations.