Drilled holes in the 12 foot 2X4s, just a few inches from either end and every 3 feet, 5 holes in all in each board. This is where we put the landscape spikes, point up. We used screws to secure the 12 foot boards to the 4 foot boards to form a rectangle.
Then just curved the PVC pipes and placed the ends over the landscape spikes. Using duct tape we taped the last PVC pipe to the top of the ribs, just for a little added support, not really sure it needs this as the PVC pipes were really not bending either direction more than a couple of inches (since the PVC pipe was only 10 inches long we did tape on a small spare piece that Jackson had in the garage, so this last PVC pipe would stretch all the way from one end rib to the last).
After that is done we just covered the shell with the plastic, put our plants inside and put some spare boards around the edges (could have easily used bricks, milk jugs filled with water etc, just something to hold the plastic down and keep it from blowing away.
This, I think will work out well. We placed it south facing and up against the brick of the house. This should help with warmth from the house as well as protection from the wind. Can easily lift the plastic to water. Will have to update in the spring, after we see if the plants survive.