So my mother visited and wouldn't let me hear the end of how horrible the ergonomics of my desk were. The desk itself is indeed tall; too tall to comfortably have a keyboard and mouse on. So even though I only spend maybe an hour every other day at the desk, I decided that the only way to make my mother stop nagging was to fix the problem. I did this by making a keyboard tray that would hold my keyboard and mouse at the proper height. It would have been much nicer if I could have just bought one of those manufactured ones off of Amazon, but that only works if you have money...so this is my solution; a custom keyboard tray.

Step 1: Gather Your Tools and Materials

For this project, you will need the following

Tools:

Hand drill (i love my dewalt) and bits
tape measure/ruler
saw (I'm in an apartment, so hand saw it is. Jig, table, or band saws would work better)

Materials:

Leg materials (I used 1x3, four 6" lengths, four 2" lengths)
Tray surface (I had a spare pressboard panel left over from a desk)
Drawer slide pair
Various screws

Step 2: Estimate Height and Cut Everything

Here's the ergonomics deal, your arms should form a 90 degree angle when typing on a keyboard. The surface of your keyboard tray should come to whatever height that is, regardless of what the height of your desk is. Make the vertical portions of the legs one inch longer than the distance between the top of your tray and the bottom surface of your desk. For my setup, the top of my tray needed to be 5" below the bottom of my desk. As such, I made my legs 6" long. (Your distance may be shorter.) I made all my legs out of 1x3 poplar that was 4 ft long. I chose poplar because I had it lying around my apartment. However, it's not a bad recommendation because Home Depot had it already sanded to a nice finish. I only had to use the sanding block to sand the edges I cut.

Cut the legs to the correct length.

Out of the same sized piece of wood, cut the 2" sections used to attach legs to the desk surface

Get your tray surface. I happened to have a 14.5"x29" pressboard left over from a section of a desk that I didn't build. Any bit of wood that is large enough for your keyboard/mouse, and thick enough to be held by 4 screws in its side should be good enough. I'd recommend staying away from MDF though; it doesn't handle screws well.

Step 3: Assemble Tray and Legs

Attach the inner race of the drawer slider to the tray board, making sure they're both pointing the same direction, so both sides will slide in unison. You may have to push down a tab in order to get the inner race to separate from the outer race.

Now to assemble the legs.

Drill a pilot hole (which helps avoid the wood splitting).
Drive a screw into that hole.
Drill the second pilot hole.
Drive the second screw.
Repeat for each leg.
Lastly drill clearance holes for attaching legs to the underside of the desk.

Step 4: Attaching It to the Desk!

One caveat, my desk is not level. If I did the easy thing and attach all the legs to the slide races before putting them under the desk, my tray would also not be level and would end up sliding out. I had to do it the hard way.

Attach one pair of legs, one on each side of the tray, preferably the front legs.
Find a box or a person to hold the tray in the correct position.
Attach the front legs to the underside of the box.
You should now be able to slide the tray out to the point that it balances, or have a person hold it so that it's even(with respect to gravity, not with respect to the desk)
Connect the hind two legs. This isn't easy, but as best you can, make sure its level when you fasten the slide to the second pair of legs on each side.
If you end up messing up your wood too much to make screws hold, there's superglue. Just don't get it in the bearings.

Step 5: Finished!

So now it slides in and out perfectly. Except that its pulling out at an angle. I can live with that because I plan to have a second monitor at an angle to my first. If this annoys you, have a second person help you position the tray while you're working underneath the desk.

My desk now has three different wood patterns, exposed drawer slides, unfinished wood, pre-existing holes in the keyboard tray, and the keyboard tray comes out at a weird angle. But I now have a keyboard tray that is actually quite comfortable, and I made it all out of spare stuff I had lying around my apartment. And my mother might find something other than my horrid ergonomics to nag about. Success!