Have a lumber store cut all plywood, alder pieces and trim to measure. Have the store miter the decorative wood trim to measure the two 8-foot sides and 6-foot top and bottom. You may also do this yourself if you own a skill saw and a mitering saw.
Sand all wood first with a medium- and then fine-grain sandpaper to remove splinters and rough spots. Stain the alder, wooden trim pieces and plywood on all sides using the disposable paintbrushes. Use at least two coats of stain and dry for at least an hour between coats. Finish with two coats of acrylic finish on all outside and trim pieces. Dry thoroughly between coats.
Build the carcass of the cabinet by drilling pilot holes in the two 8-foot sections along the bottom and top edges 12 inches apart. Always drop a bit of wood glue into screw holes when using wood screws to improve the bond. Attach the sides to the top and bottom 6-foot sections of alder. Run a bead of wood glue around the back edge of the rectangle and place the plywood backing over the carcass. Screw the plywood back to the alder.
Use the tape to measure down 3 ½ feet on the inside of the carcass and mark where the alder shelf will sit. Screw the shelf in from the outside. Make marks where the three plywood shelves will sit in the lower part of the cabinet. Turn the cabinet on its side and nail the shelf rail supports in place. Right the cabinet and place the plywood over these supports and screw them in place.
Run a bead of glue across the top of cabinet. Use finishing nails to counter sink the 6-foot mitered trim in place. Glue and nail the trim onto the shelves as well. Put wood glue down the side edges and position the side trim before nailing in place. If necessary the miter can be filled with wood putty if the fit is slightly off.
Use the drill to open plug holes in the back of the plywood. The appliance cords will feed through and be out of sight. This open-faced entertainment cabinet is now ready for the television, and all other audio/video accessories.