Measure the dimensions of your refrigerator, and use those measurements to cut your basic frame pieces. You will need four pieces of 2-by-4 material for the height of the fridge, three pieces for the width of the fridge and four pieces for the depth of the fridge, front to back. The boards you use for the height of the frame will fit under a 2-by-4 box that you will build in Step 2. Mark the pieces with a pencil and tape measure, and use a miter saw to cut the boards.
Build the basic frame on the floor before raising it in place. First assemble the top portion -- the box -- using a framing square to guide you. You need two pieces for the depth and two pieces for the width of the fridge. Form the box. Screw these four pieces together into a square frame -- or rectangular frame, depending on the dimensions of your fridge -- using 3-inch wood screws.
Attach the vertical sections to the top portion. Screw them onto the box so they form the legs of the frame. Raise it into place so that your box is above where the fridge will be, with four legs extending downward. Use a stud finder to mark the position of the studs on the wall. Use a level to guide you, and level the back section of the top box of the frame along the wall. Screw this piece into the wall studs, using the 3-inch wood screws.
Screw a bottom board -- your last width piece -- against the legs of the frame, along the wall and just above the floor. Then screw the piece into the wall studs. Attach the two side sections -- your last two depth pieces -- and screw them to the side legs along the floor. This gives you a three-sided box along the bottom of the fridge, similar to what you have on top, with the front open so you can slide the fridge in.
Measure the dimensions of your frame to cut two pieces of plywood for the sides and one piece for the top of the frame. Mark your pieces of plywood with the tape measure and pencil, and use a chalk line to snap reference lines across the sheets, using your measurements as a reference point. Cut the plywood down to size with a circular saw while using the chalk lines as a cutting guide.
Mount the plywood sheets onto the frame for the fridge. Screw the two side pieces onto the legs with the 1/2-inch wood screws. Place the screws every 12 inches up the frame. Mount the top piece on top of the box that is attached to the wall. Screw this piece of plywood into the wood box frame.
Cut down strips of plywood with a circular saw to cover the front sections of the plywood frame. Measure the dimensions of the 2-by-4 material that is visible along the front, and rip the plywood sheets into a piece that runs up the sides. Screw the strips onto the visible portions of the plywood to completely enclose the frame. Roll your fridge into place.