Okay, so we've built our cornerpiece. Now for the skeleton.
There's four uprights to be built; two will be comprised of a 180cm piece flanked by two 60cm pieces so as to form an L-shaped base with a long stem, while two will be comprised of a 180cm piece and just one 60cm piece to form an L-shaped base with a short stem.
You then join the 60cm pieces of two uprights with a horizontal beam, and one of the same length rests between the tops of the 180cm pieces. The bottom beam is secured a lot more tightly than the top beam, as it's the bottom one on which the seat rests. The ones in the rear of the skeleton need to be longer than those in the front, as the vacant space in the front forms the entrance. I used 100cm across the back two sides and 40cm across the front two sides.
The garden tends to get a little messy during a build, but I've tidied it since.