Is this what you mean?
For the first picture, you'll want to cut your squares 7". Trim each HST down to 6.5" before assembling into the final 12.5" unfinished block.
For the second picture, you would cut your squares at 5" and trim down to 4.5" before assembling.
For the third picture, you would cut your squares at 4" and trim down to 3.5" before assembling.
Unless you're making some kind of micro-mini quilt for a contest--I don't know why anyone would torture themselves making 64 itty bitty HST's just to make a 12" block.
4 HST's
[ATTACH=CONFIG]185309[/ATTACH]
9 4" HST's
[ATTACH=CONFIG]185311[/ATTACH]
12 3" HST's
[ATTACH=CONFIG]185312[/ATTACH]