Step 3: Cut the cans
The cut needs to be almost perfectly even, so use a book to hold the blade while you press the can up against it and spin. You can also nail the blade to a block of wood.
Spin the can slowly while pressing against the blade, making sure not to dent the can in the process. It will take about 10 to 20 turns to cut through it enough to peel the two parts apart.
Then use the sandpaper to smooth out the cut edge.
Once you are satisfied with the result, use the second can to gently stretch the lip of the bottom of your stove. This will make it easier to put the halves together. Finally, put some fiberglass in the bottom half only.
Once the bottom is complete, make the top of the can the exact same way, but do not stretch the lip.
The fiberglass is optional, but important. It will prevent the fuel from leaking out while moving it around or while it's in use. It will also preserve unused fuel. Cotton balls will also work, so long as the inside of the can doesn't get hot enough to burn them - a possible concern during stove use or preheating.