Here is my patio sectional made of 2x4s. Used my Kreg Jig for the first time to complete this project. I used pocket holes in as many places as possible, then finished it with two coats of leftover fence stain and two coats of semi-gloss outdoor Varathane spar urethane for a nice sheen.
I modified the dimensions to fit the cushions that my wife purchased before I began the project. I made the back substantially taller to support the cushions and left the arms off of both ends of the sectional so people could sit facing sideways too. I left the corner of the sectional without a cushion so people would have a place to set drinks.