Sewskeel, You were asking about half square triangles used in the border and in the blocks. I think this screenshot answers your question for the border blocks.
For the on point triangles to make the corners of the block, cut the square on the diagonal, stitch to the sides of the block, and then square it up.
If you slightly oversize your squares of fabric to 7 inches or 7 1/4 you can trim to perfection as Barbara Black says. It does take a little more fabric
and a little more time to square it up, but it ends up perfect. HelenW