Purchase two plastic file folder holders. You can get them at any discount or home office supply store and they look like plastic cubes in which to keep hanging file folders. Color is not important, so choose whatever looks good to you.
Place the file folder holders side by side and measure the dimensions. Add one inch all the way around.
Determine how much wood you will need for your file cabinet according to your dimensions. Make sure you account for legs and a larger top.
Purchase the wood, hinges, nails and stain or paint.
Cut the wood to size according to your dimensions.
Attach the base and four sides using nails.
Attach the top of the file cabinet using hinges.
Attach the legs.
Paint or stain the file cabinet according to your preferences and décor.
Remove the tops of the plastic file folder holders.
Place the plastic file folder holders inside. They should fit snugly.