1/8" acrylic and press fit can work, but depends on stress and strain of part. Dog bones at corners help. I’ve done some tight kerf compensation for 1/4" acrylic that holds up very well as a stationary object that isn’t going to be getting a lot of strain. But you can make them tight enough so that an iPhone stand will hold together, especially if you differentially heat and cool the parts. Not as much as metal, but it does work.
Cast acrylic is fairly consistent, especially the Proofgrade, but you do have to measure with an exact calipers. I have a tab that I made in OnShape that I print and I adjust them accordingly in the parameters to ensure a very tight fit. One thing is to choose the tab or the slot to make adjustments on. It’s easier, or you can do 1/2 kerf for each, but it means more adjusting.
So cut your slot exactly 1" x .220" in the design software. Cut your tab 1.07 x .227" sized in the design software. There are a few things to think of when doing a slot to get 1/2 the kerf on a shoulder, but one way is just print and see how it fits and then you can see what to adjust.
I do a test print and then adjust accordingly. It does make a difference in 1/4". You can only insert the tab into the top of you are going for extreme tight fits since there is a slight draft to the cut. I just print two copies of this. I believe this one is sized for a .212" thick Chemcast acrylic I have.