My kennel panels are exactly 5' wide by 10' long; I made my deck with a 2x6 treated lumber frame, used 8" long 4x4 posts in each corner, and decked it with 2x12's layed smooth face up. The deck dimensions are 5'2" wide by 12.5' long, so I do have a small "step" at the front door. I secured the panels to the deck using metal hanger wire, the same stuff plumbers and HVAC guys use to hang pipe and ductwork...just pull the hanger wire tight on the bottom rail, and screw it into the 2x6 frame. Rain and shade is provided by a 10x12 tarp that stretches from end to end, and does come over the sides to provide a little extra shade and rain protection. I am fortunate enough to be able to place it behind/under some trees, so it stays shady.
If you want to go longer, or wider, and there is even a remote possibility that you might move it, build the frame in sections that can be dismantled...this way, even if you have to remove a piece of the deck to take it apart, you still don't have to disassemble the entire thing. And, it's light emough that one guy can handle the pieces.