Afghan squares

[Bk2973]

Hi. I tried a baby Afghan squares and sewed them together. I sewed continuously horizontally then vertically. Whenever I shake the blanket the squares slides across or scrunched to one side. The squares didn’t stay securely. What did I do wrong? What is appropriate to assemble the squares securely?

[bgs]

Sounds like you used the running stitch.  You need to use whip stitch or mattress stitch.

 https://www.thesprucecrafts.com/methods-for-joining-crocheted-elements-977932