Basketball net pole

Hi all, I'm installing an inground basketball net at my house and needed some advice. I live in a northern climate so I want to have a 4 foot deep hole in order to be below the frost line. Problem is that the pole is only long enough to be set 16 inches deep into the ground (in order to have the required height above ground).

My plan was to dig a 4 foot hole and make a platform of some kind (maybe out of bricks) in the hole which the post can rest on while the hole is filled with concrete and cures. The platform would allow the pole to sit at the required depth and the concrete would dry around it forming a deep foundation.

Any other advice on this type of installation?

Thanks!