How to build above ground?

[WesselTT089]

Hey there, I am level 39 at the moment, I suck at this game and I was saving from level 25 for a big base in front of a waterfall. I discovered this spot by myself and I wanted to build a base on it. I tried everything I can think of. I have 3 stone foundations on the ground and when the cliff stops I can't build further. I have tried putting Wooden Pillars to the bottom of the little lake the waterfall ends in but that also did not work. It was a better idea to make a first real base on the surface but yes I am stupid. Does somebody know what I am doing wrong?