This is a sliding box for the right-front space under the table on the Creality Ender 3 Pro. The Pro version uses a 40mmx40mm Y-axis rail. This will not fit (without modification) on the original Ender 3 with 20mmx40mm Y-axis rail.
The stl files are for the drawer with a slide that rides on the Y-axis rail and another for the drawer using 3mm T-nuts instead of the slide. In my installation, I chose to use the T-nuts as I like the idea of being able to clamp it down. It slides just fine with T-nuts loose.
I've included Fusion 360 models as well as step and sat models so others can make use of them in the CAD system of their choice.
Edit: I also tossed in a Fusion 360 and .stl file of a rear box that works on the Ender 3 Pro. It is just a Remix of my Pi Box 4 Ender 3 without all the Pi windows and divider.
Edit 2: One user printed the non T-nut version and found it to fit so tight that the part was bent installing it. This is designed to be a snug fit. I recommend you measure your printer and modify one of the three CAD models to suit your printer. Or just print it and sand, file or scrape until it slides smoothly.
Some say, "A Maker gotta make". I say, "A Maker gotta make do". Now go make stuff.
Edit 3: I trimmed off 0.5 mm from the width of the box and called it Rev B. So it should slide easy now.
eSun PLA plus
Should slide right in after removing the support material.
I used Fusion 360 to design this. I also used an imported model of the Ender 3. I had to kind of fake it since the model I found had the 20mmx40mm Y-axis rail. I just copied and moved the Y-axis rail to make a 40mmx40mm. I could not find a CAD model of the Ender 3 Pro.