This grid of foundations will give 100% building space. Toggle "Foundations fill depressions only" to use even less foundations. This uses roughly half the foundations the game automatically uses when pasting blueprints over water. Based on full planetary blueprint.

The basic building stone is horizontal bands with 3 tiles in between and 2 tiles between horizontal bands. Two adjacent horizontal bands are 2 offset, such that the foundations form triangles.

For the small pole regions: you can copy paste smaller part of this blueprint, but I thought 20x20 was nice for general use.