On MDF I have had good success using butt joints and just glue - no screws. I like to assemble the front, sides, top and bottom all at once. It is a bit awkward and you will need some clamps. Using screws can help this - it eliminates the need for clamps. The reason I do it this way is that I get a better fit around the front baffle. Also, on MDF if your edges are a bit proud you can use a flush trimming bit on a router to just wiz them down to a nice flat finish with the other panels. Steve