Acrylic can produce a neat joint, but it should not be forced into an undersized slot. A tight fit can crack a corner or narrow strip. First decide whether the joint should slide, fit loosely or grip lightly.
Use the sheet you will actually work with
Nominal thickness is a product designation. Actual thickness has a tolerance and can differ by variant. The kerf also affects the opening. A slot drawn exactly equal to the sheet thickness is therefore not automatically a suitable fit.
Make a small fit test
Draw a strip with several slots around the expected width. Have it made in the same material and thickness as the final part. Try the actual mating sheet in each slot and record which width gives the desired fit.
Use that dimension in the final design. Repeat the test when changing material or thickness. Read more about tolerances and fit.
Avoid forcing the construction together
Leave enough material around slots and mounting holes. Do not use a screw or clamp to pull an incorrect joint into place. Support long parts where necessary and avoid loading a narrow projection on its own.
Test assembly as well
A joint needs more than one successful fit. Check that the parts can be assembled without damage and removed again if necessary. A repeatedly assembled display has different needs from a permanent panel.
Compare products in the acrylic collection and test the sheet you intend to use.