Variable Product: 3 sizes & 4 colors

I have added many variable products over the years with only one Attribute (i.e. Color – Blue|Red|Black|White …etc). Then creating as many Variations for color as needed.

Now my brain has turned to mush trying to create one product with two choices – Size & Color. Soon will have products with 4 & 5 choices.

My brain says to create two Attributes “Size” & “Color” then create 12 Variations for all the combinations. Future products will have more than twenty combinations.

How do I easily create a product that has 12+ combinations for size & color without having to create 12+ Variations?