Mine was made from 2 planks of Sycamore and a piece of dowel that once was a broom handle. Most of the plans suggest using metalwork like hinges, screws and axles; I wanted to be metal free so I used dowel. This needs a bit more precision and I needed a pillar drill for accurate holes and angles and forstner bits to get precise diameters. I also used a lathe to turn the legs from square to round. All my joints are a push fit and I glued and wedged the legs to the seat.
Since I made the thing without design or drawings I built in some adjustment for varying thickness of wood so I can use it for chairmaking or barrels or spoons. I may need to shorten the bottom jaw to hold short lengths.
2planks about 5’ long, rough sawn but seasoned. About 2” thick and min 8” wide for the bed - this has to be stiff to support the user and takes all the strain.
1broom handle, 11/4” dia. Or other dowel the same dia and 4’ length
nb. One of the designs I found in a book used a Pine scaffold board planed on all sides and ripped down the middle. If you used metal brackets and hinges you could buy all the bits you need in one trip to B & Q
Tool and facilities needed
Saw ,hand and crosscut - a power saw to do any ripping would reduce effort and save a lot of time
Plane- I removed most of the saw marks with a hand plane but its not a piece of furniture, you don't have to.
Spokeshave for shaping and a Travisher to hollow the seat. Again, this is a luxury touch and not essential. Wooden spokeshaves can be bought in many antique shops for under £10 and just need a sharpen. Power tools can be used to shape and hollow the seat - if you plan to use the seat for a few hours then its worth the extra effort.
Pillar drill and Forstner bits - not essential but where accuracy is needed its a big help.
Lathe to rough turn the legs - not essential, you can shape the legs using a spokeshave but there are loads of woodturners around who would be pleased to turn the legs from square.