Before any timber is cut for a diwan like this, the whole piece is drawn full size on a board.
Not sketched, and not scaled - drawn at its actual dimensions, in a single elevation: the sweep of the back, the curve of the arm, the line of the seat rail, the splay of each leg, all at the size they will be made.
The reason is that curves lie at small scale. A back sweep that looks graceful on a drawing an arm's length across can turn out heavy or mean when it is built at full size, and a leg splay that reads elegant on paper can look unstable in the room. Drawn full size, those errors are obvious immediately and can be corrected with a pencil rather than with timber.
The full-size drawing then becomes the working reference. Templates for the shaped members are taken directly off it, joints are marked from it, and any member can be laid onto it during the build to check it against the intended line.
On a heavily carved piece, ornament forgives a slightly wrong curve. On a plain one like this, nothing does - so the drawing is where the piece is actually designed.