I've never really tried a tutorial before, but I can give a couple of pictures I just took. Here's the link I used to build my frame:
http://www.boneyardbargains.ca/pillars.html
instead of 2x2's, I used 2x3's I wanted more support, and they were cheaper. I made them exactly 4' tall, and 17" wide. The 4' is so I could use 1 sheet of styrofoam per column.
The second picture has a second strip of 2x3 on it because I made a mistake and cut it exactly 1 board width too short... measure twice, cut once... so I lined the top with a second row of scrap...both the same now.
I'm thinking of doing the L-bracket thing, so I'll have to add some support brackets somewhere in the middle, when I figure out my fence heighth. Wow sorry the pics are so big...gotta work on resizing them...