We used the EZ Pads (4 interlocking) when we got our tub late December of last year. Few reasons, one, it wasn't going on it's permanent base as we expect to redo the whole outdoor area in the coming years and two, it was getting too cold to mess with pouring concrete. We took out the sod, dug down about 3 inches (more on one side to make it level as the ground sloped) then put in crushed stone and tamped in 2 courses and got it level. Pads on that and it's worked well. Our hot tub guy even complimented us when we delivered the tub.
