While the cases are generally shipped in small panels like this:
It is normal for parts to pop out and/or small pieces to be missing from the panels (these fall out in the laser). Please check to ensure you have the following pieces, which are all the pieces that make up the actual case parts, the rest is just scrap:
The cases are designed to be glued together, yes this means your Digispark will be stuck inside, though with a USB extension cable you should still be able to plug it in for programming.
For glue I recommend strong Acetone, acrylic glue, epoxy, or super glue - you only need a tiny bit on the mating edges.
To help assemble them here are the pieces labeled. Some sides and tops have alternative versions (for LED, for header access, for wires to leave the case, etc).
They are grouped into the four general case sizes that you can make with them, many of the tops are interchangeable between the sides.
Before assembly you should remove the plastic and/or paper film from the parts, it is only for protection in shipping.
Here are some images of a case going together, the “bottom” piece is laying flat.
The front and front edge of the bottom piece leave a gap, this is where the Digispark USB port can exit - with some of the larger cases (and even the smaller ones) you may want to glue a small piece of acrylic scrap to the bottom plate to hold the Digispark forward so the USB connector sticks out.
The paper is left on in these photos so that they show up better on the camera.
This is the “bottom” and two sides.
This next photo show the front edge where the Digispark USB connector can stick through.
Front and back added.