I made 2 mug rugs, and 2 doll quilts using 2" cut fabric for 3" finished (5 blocks) 10 minute block. Very fiddly. but, I did not curve them. They do need to be perfectly square, with exactly matching seam widths, or they get a little wonky.
If I understand you, you are using 5" charms. My experience with the very small blocks is, they tend to "hover" above the quilt. I think with larger blocks (larger even than 5") you can control the height (above the quilt) because you have more fabric to work with. Harder to control in the smaller blocks.