Great idea for a modular knit blanket. One simple shape makes a great quilt. Sidewalk Quilt by Pippa, an original design. Pattern available on her website and a similar version for sale in her Etsy shop.
FLIP & SEW METHOD (straight strips): Layer backing + batting + 1st strip RS up + 2nd strip RS down. Sew 1st seam, then flip 2nd strip over RS up. No extra quilting needed if strip is narrow. Continue adding strips and flipping them over.