I asked about this in another thread, but thought I'd make a separate thread just for this illusion incase someone else did a search or in case anyone who didn't see the last thread would have an unconsidered option.

What type of track would be best to connect the two halves of modern art so that they slide as easily as possible?

I've done it two ways. One way is using a drawer slide. This works better than you might imagine, and is the simplest/easiest way (IMO). The other way is too complicated to explain w/out pictures, but I don't think you'd want to do it this way as it takes a lot of time and math, and a bit of trial and error to get it just right. I think your best bet would be to use drawer slides.

I used drawer slides and they worked well, but it was something of a pain to disassemble and reassemble the illusion. If it will remain together, this is a great choice.

A Café member once recommended using a machined, two-piece Delrin plastic slide, using a male/female dovetail slot and tab. This works better, is quieter, and makes disassembly simple.

The dovetail slot and tab work very well just made of wood. Especially if you rub the parts with parafin wax.