One of the benefits of the Spucklerboxx design is that you can adjust the dimensions to fit the space available. I had a 6' x 8' available space, so I made my box 5'-6" x 7'-6", which gives me some wiggle room on all sides.
The original Spucklerboxx calls for the sides to be made from 3 landscaping timbers stacked on top of each other (which does look better than plain, flat sides) but those aren't available in my area. Instead, I used pressure treated 2" x 12" lumber. (note: a brand called "Wolmanized Outdoor Wood" just recently was re-released on the market --this time with the hazardous chemicals removed--so I used that instead of the typical green colored wood.)
To add stability, I had a 4" x 4" cut into 11" lengths and have one of those supports in each inside corner. It is these that the 2" x 12" lumber is actually connected to.
The key to a Spucklerboxx's ingenuity is that dang "bridge" section that spans across the top. Not only does it provide much-needed stability that ties the whole box together, but it also provides adequate clearance for the doors to set smoothly across the top. (genius! I wish I'd thought of that!) To help prop the bridge up, I used an extra 4" x4" piece in the middle as a "leg".
The doors are simple enough to construct, and don't forget to use a layer of bricks under the whole she-bang to prevent those little buggers from pulling a prison break when you aren't looking.
I suggest everyone build a Spucklerboxx without delay!