I know HST has been a topic many times but maybe my mistakes can help someone else!
First, I starched and ironed all my fabric before I cut it.
Then I cut 4 1/2 " squaures and marked the diagonal line.
Now where I made my first mistake - I chain stitched them. Stitched with the line on the left side of the foot. Then stitched with the line on the right side of my foot.
Now this is where my mistake became visible - both sides of my foot are not equal! When I laid my ruler on the line to make the cut, I found that one side was bigger than the other.
So I cut them anyhow, Pressed them open and then squared them up. I am down to 3 3/4" squares now.
One good thing happened - I glued a bit of sandpaper under my ruler so it wouldn't slip. I need to put a new blade on now but with all the problems I have been having, I think I better finish up where I am at. . . . .
What's that old saying - MEASURE TWICE, CUT ONCE!!!