I feel your pain. I just conquered these, myself. Start by making them a smidge bigger than what's called. I gave myself a 1/2" extra, then with the two squares right sides together draw a line from corner to corner. Keep your 1/4" foot on the line, down one side, then the other. Rotary cut on the drawn line, press open. Now they key point. SQUARE OFF each block to the size you need. If you are unsure how to square off, there's videos available on You Tube.
I struggled with Jenny's method, as well. Good luck, Jami!