I bought 4 pieces rough redwood 2x4 and ripped three of them down at 30 degrees and one at 0 degrees to make this frame. The angled surfaces prevent the collection of dirt and it sheds the rain. 4 lower corners using a simpson corner bracket. Sealed it with a behr sealer #500-natural before assembly. Dimensions are 4x8x2.
I accidentally bought the wrong staples for the project so I ended up using 1.25" crown moulding staples which are quite narrow. They worked perfectly! Keep in mind this is redwood, so softer (and lighter) than douglas fir.