So here goes! Prefold making 101:
*Note: All measurements are to make a 4x8x4 infant sized prefold, you'll need to scale up if you need a bigger size
You'll need two pieces of knit fabric that are 13"x30", OR one piece that is 13"x60", OR one piece that is 26"x30". I went with two 13"x30"
Measure 13" up from the last cut and cut off the top Make a thin cut along one side to give yourself a long strip of fabric instead of a tube of fabricUnfold the fabric and cut it to 30" Repeat the whole process with another t-shirt
Lay one strip of fabric on top of the other. If you did one piece of fabric, fold it in half so you have a 13"x30" rectangle that is 2 layers thick.
Keep in mind these are pieces of fabric to soak up pee and poo, they don't have to be pretty. You can see mine don't line up perfectly. If that bothers you, you can do some cutting to straighten things up at this point. Since sewing knit without an interfacing tends to stretch it out of shape a bit anyway, I wait until the end and then do some straightening.
Find the point about 3.75" from the edge
Fold the end of the fabric over so the crease is at the point you found
Now find the point about 3.75" from edge again (not the crease, the edge)Fold everything over so there is a crease at that spot you found
At this point, you should have 4 layers on the left side and 6 layers in the middle and your left side should be roughly the same width as your middleFold the right edge over so that it is even with left edge (which is now on the left side of your center portion)Now you have 4 layers on the left side, 8 layers in the middle, and 4 layers on the right side
Now you sew a straight line down each side of the middle (through the 8 layers)If you want to, now is when you'll be best off cutting the edges to make things more straight. Since knit doesn't unravel, you can be done here. Or, if you have a serger (lucky you), you can serge the edges. I have a good over lock stitch on my machine, so I just do that