Numblast

The best method is this one, where you create a "snake" combo:

If you don't understand what he is doing, here's an example of a snake combo:



I hope you see the path that starts in the lower left corner. When switching the yellow 2 and the tan 1 to make a square of 4 1s, you will do the snake combo. You have to start that path like in the video and example (lower left or right corner) with a number that you can quickly start with. If the closest is 2, start with that and so on.

Here are the starting models:



Beware starting with one of these will lock you further, if you try them all you will understand what I am saying but I will update.