I would use the x-y graph to explain the multiplication of negative numbers

I would also start with 4 x 3, then work my way towards negative numbers, e.g 4x2, 4x1 ......4x-1, 4x-2

Then I would go from 4 x -3 to 3 x -3, 2 x -3......... 0 x -3..... -3 x -3, -4 x -3

a clear pattern will be visible