The intended use of your cabinets will have great deal of bearing on the materials and construction methods used to build them. Cabinets for a garage will have less of a finish than a set of for a kitchen or dining room. Cabinet back boxes can be constructed of single face plywood or MDF plywood.
If the cabinets are intended for the garage I would use all 3/4″ thick plywood for the added strength. There are several types of cabinets such as uppers, lower, full height and so on. They all have the same basic body or shell design and differ only in size, number of shelves, hangers, slide-outs and so on. Factory made cabinets usually use 1/2 inch thick materials and then they reinforce the corners to save on costs. Doors are almost always 3/4 thick material and are then carved, routed, painted and so on.
If the cabinets are to be used in a home environment installing a face frame of a nicer hardwood material gives the outside appearance of a higher end priced unit. If a pretty face is not that important, you may construct the entire face of the cabinet of plywood.
When laying out the cabinet pieces on your plywood for cutting, try to use every inch of the plywood that you can. All doors from one sheet, backs from another and so on. If you have a biscuit joiner, using biscuits along with screws and good glue can make a super strong cabinet.
Once all your panels are cut to size, cut your biscuit holes and start assembly of the cabinet boxes. Whether you are using plywood for the face frame or intend a hardwood face, you must clamp the boxes during drying. Pipe clamps are cheap so make several sets if you do not have them on hand.
Clamp ends are available at your hardware store and the pipe parts are simply black plumbers pipe. Pipe nipples are available in twelve, twenty-four,thirty-six and forty-eight inch sizes in most larger stores already cut to size but they will cut you pieces any length of pipe you need.
Once the main box is constructed the face frame is next to install. The face frame should be fastened only with biscuits and glue and perhaps a couple of very small finish nails if you are staining the cabinets. If the cabinet is painted, countersinking the nail heads and using wood putty will conceal all your nails.
If you are using 3/4 inch plywood, additional interior stiffeners are not necessary unless you intend to store very heavy materials. Adding a small extra strip of plywood at the rear of the cabinet, at the top and bottom, will allow you to screw through an 1 1/2 inch thick piece with larger and longer screws giving added support.
Doors can be mounted either with a surface mounted hinge or what is called a European hinge which is fully concealed when installed. Lay the cabinet on its back and then adjust the door to assure the reveal on all sides of the door is the same. If the door is a full face door, make sure it is even with all edges of the cabinet.
Mark your hinge locations and install the hinges. European hinges require the use of a “bottoming” bit that has no brad point on the end of the drill bit. When the door is drilled to accept the hinge pocket, you do not want the drill point to pierce the front face of the door. If you have a drill press this is an excellent tool for drilling the pockets as it keeps the bit from wandering during the drilling process.
Time now to sand and paint or stain the new cabinets. Whether the new cabinets are full height for a wall oven or a short twelve inch high unit over a fridge, the construction remains the same.