How can I make a spiral staircase with basic blocks at right angles?
Based on the limited brick options, and the "it needs to be solid" constraint, I present my "Minecraft Spiral Stair" in LEGO form, and to provide "inifite height", I've gone for a "hung" support option:


Start with two 2x2, a 2x4 and a 2x6 in this configuration:

Add more steps as you need rotating around the lower 2x2 brick:



(Key: Yellow: 2x2, Blue: 2x4, White: 2x6)