For less than $10.00, you can put the whole thing together in about 30 minutes.
I made it at TechShop! I have a router table / saw at my house, but my shop is cramped and it's tough to deal with 8' 2x4s. Doing it at TechShop made it a breeze to put this together!
Step 1: Route two 3/4" slots in two (2) 2x4s
Cut one of the 2x4s to a length of 3 feet.
Route two slots along the entire length of the 3' 2x4.
On the other 2x4, route two slots about 3 feet from the end.