Place two equal sized squares right sides together .
Sew all round 1/4inch seam allowance.
Top square snip this one only and cut across diagonally.( take care not to cut square below)
Press out.
Take square same size as the new square and sew all round
Cut diagonally on top square only.
Press
Keep going to a block size.
You always loose the points which I wish I could sort out.
Hope these instructions help. I was never given specific square sizes only make new square same size as one just pressed.