The pattern suggests worsted weight cotton and that will yield a square that is approximately 8-9” depending on the knitters gauge.

It can be made smaller by using DK weight cotton yarn and appropriate size needles to get a nice tight knit to make the stitches pop. The same is true for a larger size for a pillow or throw. Use thicker yarn and appropriate size needles to yield a close knit fabric.

Happy Knitting!
Alli