The first thing you need to do is take apart the draw slide. On the back there should be some tape that you need to pull off. Where the tape was is a part that you can slide off, remove it. You won't be needing these pieces so you can toss them away.

Now you need to separate the slide into its three parts which I call the Large Slide, the Slider, and the Small Slide. To do this you need to fully extend the slide. Once you have done this you'll notice a notch in the Large Slide that prevents the other pieces from falling out. You need to remove this piece in order to modify each piece. In the photo above you can see where I cut Large Slide, the angled cuts are purely for aesthetics so it doesn't matter if you prefer to cut straight down. Just make sure to keep the hole within where you cut so that you won't have to drill another one.

Once you have removed this notch you should be able to slide each part out. MAKE SURE THAT YOU HAVE A CONTAINER OR MAGNET TO CATCH ALL THE BALLS WHEN YOU SLIDE OUT THE SLIDER.

Take the Large Slide and measure out 9 7/8" (if you go with 10" it's not a big deal, I'm just going with what worked for me the first time). Once you have marked it go ahead and cut it. Make sure after all your cuts you grind down the edges to make it smooth.