Attach the two together using keg screws and wood glue.
Repeat this process on the other side of the 2714 piece.
Do this on the back of the side frame piece as well.

Image Credit: Angela Marie Made via YouTube
Then, repeat all of the above processes for the second side frame piece of the couch.
Repeat this process for the second side frame.
Add pocket holes on both ends of the remaining 6 pieces of 2714 and 5 pieces of 5712 boards.

Attach the bottom frame to the side frames 10 up from the ground using Kreg screws and wood glue.
Add the last 2 pieces of 2714 boards on the bottom frame.
fill the holes with stainable wood filler, sand if needed, then stain your wooden couch.

*All these images are credited toAngela Marie Madevia YouTube.