>>How do I make a pyramid that will fit on a base block where all the sides match?

The pyramid is inscribed inside the base diagonals. (Create a circle around the pyramid points and you will see the circle is tangent to the four edges).

To get a four sided pyramid to match the four edges, create a pyramid using the diagonal method, then go back and modify the diameter. To calcuate the diameter that will match the edges, measure the distance between the two diagonals and use this as the diameter.