Drive two stakes into the ground ten feet apart where the end posts of your fence will be. Tie a piece of mason's twine tight between them. Measure from the left hand stake eight feet along the twine and wrap a piece of tape around it to mark the spot.
Mark the ground under the tape and at the base of each stake with a squirt of chalk from a chalk line chalk bottle. Dig a post hole 24 inches deep and 10 to 12 inches across in each of the three marked locations. Stand an 8 foot 4-by-4 treated lumber post in each hole and fill the hole with 1/2 bag of dry concrete.
Stand the first panel in place between the first two posts. Attach the panel to the right end post, with two 3-inch treated deck screws through every horizontal rail into the post, so that the edge of the panel is flush with the outside of the post.
Drive one wooden stake into ground 2 feet behind this post and attach a 2-by-4 to it with a single screw. Lean the 2-by-4 on the back of the fence panel. Stand the second post up and align the end of the panel in the center of the post, vertically. Attach it as you did the first panel, two 3-inch screws through each horizontal brace.
Finishing the Fence
Drive in a second stake behind the second post and attach a 2-by-4 as before. Use a level to stand the fence upright, level front to back. Attach the loose ends of the two 2-by-4 braces to the two posts with 3-inch treated deck screws to hold the fence upright.
Add water to the concrete in the first two holes and mix it to the consistency of oatmeal. Fill the tops of the holes with dirt and pack it down with a soil tamper.
Measure and cut a 2-foot wide piece from the second panel with a circular saw. Fit it up to the first panel and align the last post so that its outside face is flush with the outside edge of the panel. Attach the panel with 3-inch screws as before.
Add water to the last post hole and mix the concrete. Pack dirt into the hole and tamp it down. Allow the concrete to harden for 24 hours, then remove the braces and wooden stakes.