The Podium feet are a sort of hard rubber. It can slide on hardwood but not easily, not unless your speaker is very light.
The thing about them is each corner is a spring that must be free to move in all directions. Because of this they don't slide around like anything normal you would be familiar with. It is best to put them right where you want them to be, and then put the speaker on them. The included instructions are clear on how to set them up and get them perfectly level.
Your speakers aren't attached, they sit on the Podium. Same as they would sit on the floor. No difference. The springy rocking only happens when you tap them. In normal use even playing music quite loud the speakers do not move at all. So no reason for them to be attached.
Mine are on BDR Cones with Round Things, exact same as what I was doing before. Only now the whole thing is on Podiums. You can see how it looks here
https://systems.audiogon.com/systems/8367 You can also use furniture gliders or other similar stuff under the Podium feet. Mine are on BDR Round Things, and there are others using different sorts of gliders there. They are pretty flexible in terms of it depends what you like and what kind of floor you have.
One of the best parts is once you get them on there it is super easy to get them precisely level. Before using Podiums I had to use shims and even then it was hard to get perfectly level. With Podiums the knob at each corner turns silky smooth and getting them level is easy and fast. Best of all once you do get them perfectly set up and level they stay put!