There are several composting structures available such as this unit that features air vents along the sides and is made from recycled plastics (figure A).
You can also assemble a wire bin from fencing materials (figure B).
Compost tumblers rotate to turn and mix the organic materials (figure C). Building your own composting bin:
Materials:
2' by 4' pressure treated wood
2" by 4" welded wire
2 ½", #8 galvanized deck screws
3/4" galvanized staples
3/8" by 6" long carriage bolts
washers
tape measure
gloves
wire cutters
drill
saw
hammer
wide wood chisel
Steps:
1. Measure and cut six, 2" by 4" boards 48" in length.
2. Measure and cut six, 2" by 4" boards 45" in length.
3. Pre-drill the holes along the corners and fasten them together using 2 ½", #8 galvanized deck screws to create a tight joint along the corners. Connect all four sides to make a square shaped frame.
4. Measure and mark 4' in length along the wire, and cut to size. Be sure to wear gloves.
5. Place the wire on top of the wooden frame, and use 3/4" galvanized staples to fasten the wire in place. Start in the corner with the wire positioned flush with the frame corner edge. Secure a staple in place about every third wire to hold the wire taut.