Sewskeel, Barbara answered your question, but for those visual learners. Here is the screenshot of one of the numbers she posted for finding the sizes to cut squares for
triangles. I put a green arrow pointing at the number of the post. As she said each post gets a number. It does take a few minutes to scan back to the correct page.
You mentioned for half square triangle blocks on the outside borders. Be sure the bias is on the long diagonal of the triangle. You get that with making half square triangles.
If you cut larger squares into quarter squares, you bias will be on the outside of the block edge and it will more than likely cause waves and wonkiness on your borders.
HelenW