Here are the items you will need to complete a useable couch!

-any full block you want your couch to be made out of -any half slab you want to sit on

-3 soulsands -3 minecarts-1 redstone torch -1 piston -3 pieces of rail

-3 dirt blocks-2 stairs

http://prntscr.com/1y4w3u

Lets get started!

1-place the soulsand in a line on the ground http://prntscr.com/1y4usb

2- place the full blocks around the soul sand like this http://prntscr.com/1y4vne

3- put half slabs on top of those full blocks like so http://prntscr.com/1y4vtx

4- put the stairs beside the 3 soul sand like so http://prntscr.com/1y4w7k

5- place the 3 dirt blocks on top of the soul sand http://prntscr.com/1y4wfs

6- place the 3 pieces of rail on top of the dirt blocks http://prntscr.com/1y4wxv

7-place 1 mine cart on top of a piece of rail http://prntscr.com/1y4xfrthen remove the dirthttp://prntscr.com/1y4xojrepeat the process for the other 2 dirt blocks http://prntscr.com/1y4xzl

8-place the piston one block away from the mine cart then place one half slab between the mine cart and piston http://prntscr.com/1y4ywp

9-place redstone torch behind piston http://prntscr.com/1y4z6ythen remove piston and torchhttp://prntscr.com/1y4zc9repeat process for the other 2 minecarts http://prntscr.com/1y4zl8

Enjoy your couch!