Cut out and label the MDF bar panels. The front panel should measure 84 inches by 42 inches, the two side panels should measure 42 inches by 22 inches and the top bar surface should measure 96 inches by 28 inches.
Cut out the 2-inch by 4-inch support brackets. These should include four 42-inch lengths, four 17-inch lengths, two 84-inch lengths and two 35-inch lengths. Cut down four 4-inch by 4-inch posts at this time to 43-inch lengths as well.
Nail the support brackets to the sides of your bar panels using 2 inch nails. Lay the side panels flat on the ground, then place two 42-inch long 2x4s on each 42-inch long side of each side panel, and nail through the 2x4s into the MDF. Place the 15-inch long 2x4s along the other edges of the MDF panels, inside the ends of the 42 inch long 2x4s and nail into place.
Nail the support brackets to the front panel. Place the front panel MDF sheet on the ground, then lay and nail the two 84 inch long 2x4s to it along the 84 inch long sides. Place the 35 inch long 2x4s on the other edges and nail them between the ends of the 84 inch long 2x4s.
Place two 4x4 posts under the 42 inch long sides of the front panel, flush with the top and side edges, 1 inch overhanging the bottom and nail into place through the 2x4s, MDF and into the 4x4s using some 4 inch nails.
Stand up the front panel and place the side panels over the 4x4 posts and nail through the 2x4s, MDF and into the 4x4 posts using some 4 inch nails so that the top of the side panel is flush with the top of the front panel, and the 4x4 post is hidden inside the corner between the front and side panels. There should be a 1 inch foot of the 4x4 posts exposed on the bottom of each corner.
Nail through the back edges of the side panels into the two other 4x4 posts to stabilize your three-sided bar onto its four upright posts.
Place the top bar panel over top of the now constructed frame, and measure a 6-inch overhang over the front panel and each side panel. Nail the top to the bar using some 4 inch nails into each of the four 4x4 posts.
Paint or stain the wood surfaces of your bar using some wood paint or stain of your chosen color.