Go to the next step for necessary pieces and tools.
Step 1: Materials
4 - 16 inch 2x4
4 - 13 inch 2x4
8 - 1/2 inch washers, or any size washers that suit you
2 - 3 inch PVC couplings
2 16 inch squares of plywood. I used 3/8 inch. Use what you want.
wood screws (for the base, I used 6 X 3/4 and for the frame itself I used 2 X 8)
maybe wood putty
paint (if you want)
I will say, that I have found my construction grade lumber to be disappointing. There were cracks that were hard to drill through or put a screw through, hence the wood putty being needed to hold the wood together. At one point, I just used my shorted wood screws I am using to attach the base, to keep the wood together. I also had a spot where the split resulted in the wood missing a chunk, so I had to rebuild it with wood putty. In addition, when I did that, I had a little bit left over, so i filled in all the screw holes. It is really simple to make too! You just need a drill, with drill bits and screw driver heads. And maybe a saw to cut the wood if you want, but I used a rotary tool to cut my plywood. The choice is yours
Step 2: Wood
I got my wood cut at the store, they charged an additional 7 dollars, but my only other option was by hand... which wouldn't be precise, so it was worth it for me. If you cut your own wood, you could try having mitered joints, where you would need a total of 8 16 inch pieces, but I went with the end to end.
Before I drilled. I used the end of a 2x4 to mark off the area on the wood where it would contact the other 2x4. Then I drilled 2 holes in each end to make it easier to put together.
Step 3: Make the Box
If you end up using wood putty, you can fill in your screw holes. I did because I had a bit extra made and decided to use it up instead of let it dry.
You will want to cut your plywood into 2 16 inch squares. How you do this, is up to you, be it a table saw, jigsaw or whatever. I used a jigsaw. You then use smaller wood screws to attach the plywood to your frame. You can sand the edges if you want.
Step 4: Washers and PVC
IF YOU WANT TO PAINT THE BOXES, do that before you put the PVC in, because it will be much much much easier. Also, sand sand sand sand the entire thing. I didn't sand the inside bottom, and when compared to the outside bottom, I really wish I did.
I then attached the PVC connector inside the center of the box. I used gorilla glue, but you can also use epoxy or whatever you want to secure it to the wood. try to center the pipe as much as possible.
There really is not too much more to do, but there are different things that can be done to the design.
Step 5: Other Ideas
You could have miter joints, which requires more wood
You could use a higher grade wood, where you might be able to stain it then
You could use other thickness' of bases
Be sure to upload pics if you make it!