I started with the back of the cabinet. I cut 2 feet off a 4X8 sheet and then framed in the 6X4 foot remainder. I left a half-inch lip on both sides and top so as when the sides and top are attached they would be flush to the back sheet. I didn’t leave a lip along the bottom because I will be making a hopper that will screw directly to the 2X2. Here is a picture of that back finished.
Next was the side of the cabinet, the right side. I will cut out an opening where the door will be and parts passed through later. I ran 2X2 around the bottom and front of this piece and left the back without frame so that it will bolt up to the backside of the cabinet. I put the 2X2s flush along the front of this piece because I want the front sheets to not show seams. I just think that it would look nicer this way is all. I had considered putting an angle on all of the edges and have no seams at all but I just don’t have the patents for this or a router to do it. Here is a picture of the right side with no door cut out.
Now I had cut the opening for the door on the right side and I made another mirror image, minus the opening for the door, of the right side for the left side. I attached them to the back panel with stainless drywall screws. At the corners I added additional screws to make them even stronger! Next I started on the top. I needed the top to be done so I can start to get the structure solid. I cut a 2X4 with a 25-degree angle on my table saw all the way down it. I tried a 2X2 but there just wasn't enough left of it to be solid so I used a 2X4. This will allow me to bolt the top and the front to one piece of 2X4. I screwed this angled 2X4 to the top front of my cabinet. And of course here is a picture of all that.