Many years ago I made my 3 year old wooden letters to help him learn to read. I went to a stationary shop and bought templates for 5 inch high letters. I simply used them as templates and they worked nicely. Seems to me that they should still be sold. They had several different sizes.
Numbers were available as were different shapes, circles, triangles, squares, half moons, etc.
Now they probably have all that online, never thought of that at first, but should have.