Screw through the drawer sides to the bottom of the drawer. I'd suggest waiting to add the top panel until the drawer is mounted so there is more wiggle room if the spacing (1/2") for the drawer pulls is not perfect. To ensure my drawer pulls were installed perfectly level, I used my level (which could easily be a straight piece of wood around 2" wide) to draw a straight line on the inside of both side panels. Then set my newly assembled drawer base on a small stack of papers (around 15 sheets under each side) to simulate the bottom clearance of the drawer. Once the drawer was offset by the stacks of papers, I used the same level to draw another line across each side of the drawer.

At this point you're ready to mark the holes for mounting the actual drawer pulls. Note the holes could vary depending on the drawer pulls you use. At the completely closed position, the front of the drawer side panel should be exactly 1" from from the very front of the side panel (meaning once you add the 1/2" drawer front, it will be 1/2" from the front of the side panel). The drawer pulls in the materials list had a travel length of 9 9/16" but only needed 7". The extra length allowed me to pull the drawer out enough to adjust cables without removing the drawer entirely, which was handy.

Once you've attached the drawer pulls using 1/2" screws or shorter, install the drawer. If it moves smoothly and you are happy, you can attach the top and front panels. In my case the bottom of the drawer would lightly graze the bottom of the cabinet. But not to worry, attaching the front panel straightened that out. For ease, I attached the front panel to the top first, then mounted as a single piece to the rest of the drawer. If you feel your side clearance is too tight for the top panel, you may want to use a router to shave a millimeter or two off each side. I did this by using a straight piece of board as a guide and once again used the trim bit with bearing.

Before assembling the rest of the drawer I screwed the monitor panel directly to the top of the frame using SPAX screws. No need to tighten them completely; you will be removing them again. I'd suggest one screw in the top center, then one in each side panel near the bottom of the monitor panel. The monitor panel should measure 1/2" from the edge of the side panel all the way down. To make sure of this, take (or cut) a small straight scrap of the MDF to use as a spacing guide before screwing the panel to the sides.

Before attaching the top of the panel, drop a joystick in place and mark the 4 mounting holes. Then pre-drill holes with a 3/16" bit for each joystick.

Finally attach the top and front panel using the SPAX screws. I suggest starting with the front panel and making sure to put a screw in the middle of the front panel to help support the drawer. It's probably best to attach while the drawer is installed to make sure it's installed in it's natural position. The front panel is suppose to be longer than the drawer to act as a handle when pulling out the drawer but this means you'll have to reach under and help straighten the bottom of the drawer if it is bowing so that you can screw in to the front panel while it's straight. After that, a couple more screws on the front and top should be plenty. Then test that the drawer does not graze the monitor panel when going in and out. If so, you may need to trim more off the bottom of the panel.

Suggestion: Something I did not do, and wish I had, was round (either by hand or with a router) the edge of the control panel so that your hand would not rest on a hard edge as you play.