This bench can comfortably fit 2 people and a third one if needed. It is made without any screws and just uses wood glue and wooden dowels. The back rest is foldable, so it is more compact when stored away

Supplies

I used pine wood from my local hardware store.

4x 60x10x10cm (for the feet)
2x 120x10x10cm (for the longside connections)
2x 30x10x10 (for the shortside connections)
2x 55x10x6 (for the arm rests)
8x 15x40x2 (for the seating)
2x 40x10x6 (for the side poles of the back rest)
1x 108x10x6 (for the longside connection of the back rest)
2x 108x15x2 (for the the back rest)
4x 17x2x2 round stick (for the conenction of the back rest to the body)

as well as a bunch of wooden dowels and wood glue

Step 1: Cut All Pieces and Prepare the Joinery

I decided to give the construction more stability by doing a cutout at the feet posts to rest the horizontal posts in. I am not sure how this joinery is called, but it gives it extra strengh, because the weight can rest on the cutouts rather than wooden dowels or screws.

To cut out these 2cm pockets I used a hand saw as well as a chisel. I also give the horizontal beams a 2x2 45deg cutout on the corner where they meet.

Pro Tip: To get the exact depth of 2cm with the saw I marked it with a sharpie on the saw, so I knew when to stop.

The second joinery i made was a inlet for the sitting surface. With a hand router I cut out a 2x2 pocket on the horizontal beam, so the wood for the sitting area would fit in nicely.

Step 2: Connect the Parts

I used clamps and tension belts to hold everything in place while I glued the parts together.

Step 3: Connect the Back Rest

To connect the back rest I first tried out what a comfortable angle would be for my usecase and then cut some 20mm hole for the round wood to fit in and connect the back rest with the body. The back rest is just tall enough so the top round sticks can be removed and the back rest folds down perfectly. In this state it can be stored away nicely.

Step 4: Give It a Paint Job

I gave it a red-brown hardoil coat for a nice look followed by an oil-wax outdoor mixture to keep it protected from the weather. My girlfriend also engraved our family nickname into the backrest with a soldering iron.