I completely forgot to take pictures of the old fire pit (it was just a bunch of big rocks laid out in something approximating a circle), as well as the digging and leveling that I did before I poured in the gravel. Long story short, dig a hole roughly 5' in diameter and nine inches deep, and level out the bottom of the hole as best as you can. Make sure you use an actual level (4' level FTW) and don't try to eyeball it, as the surface of your yard is probably not terribly level to begin with.
I bought and assembled a heavy duty wheelbarrow for this project. You absolute do not want to try doing this kind of project without one! If you don't already have a wheelbarrow, I'd recommend buying one that has two wheels as you're going to be moving a lot of weight. I bought this wheelbarrow as part of a "mix and match" kit (you buy the tray, handles, and wheels/accessories separately and have multiple options for each) at Menards for about $100, but there are plenty of cheaper options.
After leveling the bottom of the pit and checking depth throughout, start adding gravel. It took me 25 bags of 3/4" drainage gravel to add get ~7" of depth. Each bag is 0.5 cubic feet. Use a steel-tined gardening rake to keep the gravel level, and double-check this using the 4' level mentioned earlier.
Here's a quick shot showing the finished hole filled with gravel and all of the bricks needed to build the walls of the pit.
I completely zoned out on providing pictures of setting the first course (row) of bricks. The fire pit comes with instructions that show the ordering for each course and how to offset the upper courses from the previous course. The first course is the most important. Each brick needs to be leveled from front to back, as a minor forward or backward tilt can result in substantial gaps as the courses stack up. Bricks also need to be leveled across the course (e.g. from the 12:00 brick to the 6:00 brick) to make sure the entire pit doesn't end up crooked, but this shouldn't be a problem if you leveled the base of the hole and the gravel before building the wall. A heavy rubber mallet is very useful for this stage of the project.
The bricks within a course are not glued together, but each course is glued to the one below it as shown above.
Here's a shot of my beautiful wife laying down the final bricks. I couldn't have completed this project without her help!
I used a battery-powered Ryobi caulk gun and six tubes of landscaping adhesive. The battery-powered caulk gun is reeeeally nice to have, but completely unnecessary if you don't other projects requiring one.
Here's about half of the dirt we dug out of the pit. It's amazing how much dirt came out of that hole. One of the hardest parts of the entire project was figuring out where to put all of this dirt when we were done. I filled every hole in the yard, placed some near the base of the garage, and threw a bunch of it at the base of our trees. You can also see the sticks that I pulled out of the old pit, and the stones that used to ring the old pit in the background.
Here's the finished product. Once the last course of bricks is set, the fire ring is inserted. Just in case 12.5 cubic feet of drainage gravel wasn't enough, another 2.5 cubic feet of pea gravel is added to the bottom of the pit. This finer gravel allows ashes to be washed down with a hose while retaining any unburnt material. I filled in the exposed drainage gravel outside of the bricks and seeded it with grass seed and fertilizer, so hopefully it will look better in a few weeks!
So there it is. This is the "Ashwell" fire pit kit from Menards, which costs ~$500. They have much cheaper kits as well, and there are a variety of shapes and sizes available. The kit includes the bricks, steel fire ring, 5 tubes of landscaping adhesive and 5 bags of pea gravel. The 25 bags of 3/4" drainage gravel were not included and cost ~$125.
You'll also need a good shovel, a wheelbarrow, a caulk gun, and some decent gloves. I also used a tamper, a steel-tined garden rake, and a hoe (insert Wes's Mom joke here), but these tools aren't strictly necessary.
-b0b
(...exhausting, but totally worth it!)