I agree with Nora. I am sold on anything created by Deb Tucker. She has two sizes. The big one is expensive, but it does blocks that finish in whole inches from 1 to 12, and can do nested SIS units. The smaller one will do 1 to 6 inch blocks but I don't think it does the nested.
https://deb-tuckers-studio-180-desig...square-squared
Paper piecing is also a good option if you don't want to wait for a ruler.