Build up crochet afghan   

convert this to crochet

 Chain 6, double crochet in 3^rd, 4^th, and 5^th chain from hook, chain 6, turn work, slip stitch in space between chain and first double crochet of 1^st Row. chain 3, 3 double crochet in the space between chain and 1^st double crochet.

It will end up looking like a triangle until one side shows you how big and wide the square would be when done.

To decrease rows

When one side is as big as the square is that you want, turn work and slip stitch in the top stitch of the chain three space. 3 slip stitch in the three double crochet, slip stitch in chain 3 space, chain three, 3 double crochet in same chain 3 space. Continue until you end up with 3 double crochet and tie off.