Cut the pieces for the front, back and ends from 1" x 8" boards. Use a circular saw or table saw when cutting the pieces for your planter.
For the front and back, cut or plane a 5-degree bevel along the bottom edge of each piece.
To make the ends, cut two pieces of 1" x 8" wood to be 6" wide. This will correspond to the height of the end. Then cut the sides of these pieces at an 85 degree angle to create a 5'' and a 7'' base on these two trapezoidal pieces.
To create the bottom, set the saw's bevel adjustment to 5 degrees, and cut a piece of 1'' x 6'' so that it is 5" wide. Use a plane to bevel a 5 degree angle on the two lengthwise edges. Next, cut the bottom piece 3/4" shorter than the length of the front and back pieces so it will be recessed 3/8'' and fit properly with the front and back when assembled.
When using a circular saw, be sure to wear protective eyewear and wear a facemask to prevent you from inhaling sawdust.