When hand quilting, make sure your needle. Goes thru all 3 layers. I hand quilt, and use a quilting/between size 11. Its a small needle. Play with different size needle. I think, my 1st hand quit top. I made, I used, I think a #9 or 10 for sure. But got introduced to 11's, and I'm hooked with them. As for you plain sq's, maybe you can go to a shop. And find a size for that sq. I've got a Dble wedding ring quilt, that I'm going to hand quilt. And I went to a quilting shop, and they pointed out a template to fill in the center with.