Method of Multiplicating arbitrary numbers 3 * 3, 4 * 4, 5* 5...

I only know the Generalized Trachtenberg Method using inner sum, now is there any other alternatives appropriate to 3 * 3, 4 * 4, 5* 5, … speed calculation? I want to try other methods to find what fits to me. I’m going to use Memoriad Mental Multiplication program to train.

There have been so many topics about multiplication in the past, it is best to do a search on this site:
Search multiplication

Let me know if you have specific problems.
I can always help.

IMHO, it is best to start with a generic way of miltiplication:
Criss Cross