The bed ended up 2m deep and 2.7m wide, comfortably sleeping four people. It is also modular - if I move to a place which won't be big enough to hold it, only one part can be used, leaving me with a 2x1.8m king size bed which is still quite ok for 3 people. Those sizes are determined by the sizes of mattresses available on the market, and can be reduced if instead of a king size mattress you want to go for a queen or double.
Additionally, the bed has a couple tweaks to suit our kinky lifestyle. One major one - it serves as a support for my bondage suspension frame, visible in the pictures. Of course, the bed can be made without such extra features in mind.
Step 1: Materials and tools
5x 2060 x 44 x 44 (posters)
1x 2060 x 70 x 70 (frame support poster)
2x 220 x 120 x 20 (KS support boards)
2x 1952 x 120 x 20 (bottom sides)
2x 1952 x 20 x 20 (bottom side support)
1x 2000 x 120 x 20 (bottom inside KS)
1x 1946 x 120 x 20 (bottom inside KS-S)
1x 1970 x 120 x 20 (bottom inside KS-S 2)
1x 1726 x 120 x 20 (bottom front KS)
1x 1732 x 120 x 20 (bottom back KS)
1x 860 x 120 x 20 (bottom front S)
1x 880 x 120 x 20 (bottom back S)
2x 1952 x 100 x 12 (top sides)
1x 1946 x 100 x 12 (top inside KS-S)
1x 1726 x 100 x 12 (top front KS)
1x 1732 x 100 x 12 (top back KS)
1x 860 x 100 x 12 (top front S)
1x 880 x 100 x 12 (top back S)
18x 1800 x 40 x 8 (mattress support KS)
18x 900 x 40 x 8 (mattress support KS)
If you are going to put the bed to some heavy testing (more than 6 people in it, especially if they are having sex), I recommend getting several additional 220x120x20 boards to use as additional support for the bottom side boards and 140x120x20 for the bottom inside boards.
c. 40x 100 x 5 (for most boards and poles)
c. 100x 20 x 3 (for mattress support boards and attaching the central support in KS)
4x 60 x 6 bolts with nuts (for attaching the S extension)
4x 70 x 70 corner braces (for attaching the central support in KS)
4x 50 flat braces (for attaching the central support in KS)
4x king size duvet covers, or any fabric which will cover the surface of twice 2x2.7m, twice 2x2m for the sides (allow some extra fabric for the ruffles) and one 3x2.3m for the canopy.
Wood stain and varnish (about 1l each)
Files and sanding paper
If you will get all the wood cut to size in the shop, you won't need a saw, but I guess it's always good to have one in case anything needs adjusting.