This is a nice, quick and easy to print model that can hold any standard slides, with a basin length of 77.5 mm and a width of 26.5 mm. Designed to have just a little bit of wiggle room if the slides are imperial, 3" x 1", like the VWR slides I currently have.

I print these at 0.08 mm just to get a really well defined slope on the middle area. Probably not necessary though. 

To keep it in place, I simply used some lab labeling tape and stuck it to the bench. Works perfectly.