Obviously, you need a window that faces South and gets a lot of direct sun, especially in the cold winter months. This is the window in which you place your panel, but you knew that already when you measured your wood for a custom fitting frame.
Placing the Pop Can Solar Furnace
Since you've already measured your window, custom built your frame AND checked to make sure everything fit before placing your cans, there should be no issue with this step. Simply line up your panel at the bottom of the window. Make sure your haven't mixed up your top and bottom. The worst thing that could happen at this point is to have your cans all fall out as you reach the end. Go gently and you should have no issues if your cans are snugly fit. If not, go back and shim them further!
Simply lift the panel in place. In my case, it was a snug and perfect fit, so I didn't need to tack it or anything. Do whatever you need to do to ensure it doesn't fall out! You will likely want to remove the entire panel next summer, so don't permanently attach it to your window frame.
Just in case you're concerned, this is what your neighbours see when they see the pop can solar furnace from the outside of the house! As you can see, I just missed the last few minutes of direct sun today. Hopefully, tomorrow will be sunny and I'll be able to report how it works!
(See the results!)