I just wanted to share a little adaptable method I've been using to mount various robotics components without two-way tape, zip ties etc.
It is quick to adjust the size (within a certain range) and holds surprisingly well when the center screw is nice and tight. It is worth noting that you could also use springs, o-rings, or rubber bands across two of the tips to hold it together instead of relying on a tight center screw (though I have not tried it since this works out pretty well).
I used plastic beams but aluminum beams would work just as well and probably look cooler. They range in length from 1.54" up to 12.32" on ServoCity.com. The beam length you need will of course depend on the size of the item you are trying to hold.
There are a variety of grommets available, I experimented with 3 different styles.
For electronics boards I really like the 9600K53. Electronics boards fit very nicely in the slot between the top and the bottom.
The tall and thick 9310K16 has a nice combination of being sturdy and soft... I've used it for batteries and phones.
I press fit the grommets onto 1/4" OD 6-32 tapped standoffs. The length of the standoff depends on which grommet you go with. I used a 3/4" long standoff (534-3488) for the tall 9310K16 grommet and I used a 1/2" long standoff (534-3487) for the shorter 9305K32 grommet. Though the 9600K53 (the one with edges that hold electronics boards nicely) has a larger inner diameter so I needed to use some 3/8" long #10 nylon spacers (561-KSP172) instead of threaded standoffs, which meant I also needed some nuts for that one.
Since one beam will be a beam's thickness is higher than the other I spaced up 2 of the 4 grommets with 1/8" long #6 nylon spacers (0.14" ID , 0.25" OD) so that they are all about even.
Join the two beams by simply putting a screw through the middle hole of each... I put another nylon spacer on the bottom to account for the height of the screw heads at the tips.