Now that the concrete is dry enough, it was time to build the deck foundation.
It’s 12×12 ft (3.66 meters) and the hot tub will be positioned in the center, leaving space to walk around it or even put some chairs there. 
The hot tub was delivered here today (Amazon now does deliver in my subdivision; two years ago they still left things at the post office for pickup).
I will probably unpack it and have a look tonight.
Today I started on the deck for the hot tub. It’s on the west side of the lodge, as that’s a spot with a little privacy. Theoretically the hot tub could go on the main deck, but this seemed like a better spot.
From upstairs you see the layout. You may be able to spot some lines, and the concrete base with rebar reinforcements. The forming tubes will be used to create a base on which the 9 4×4″ posts will go. Once the bases have dried, I can put the 4×4’s in place and using a laser, cut them to form a perfectly horizontal support. On those 4×4’s there will be 2×6″ joist every 16 inch. That should make it strong enough to carry the weight of a filled hot tub with 4 people in it. The deck is larger than the tub; for now I will start with an inflatable 70″ hot tub. If at some point in time I want to place a nicer one, I can use the same deck.