A pre-Christmas sale brought a cheap SSD that rendered my oath not to install one in the Lenovo Q150 inoperative, so I had to figure out how to open the case. Removing the visible screws didn’t release the cover, but some exploratory prying eventually popped the internal snap latches. Knowing the latch & screw locations will simplify harvesting the SSD when that time comes…
Front (with USB & SPDIF jacks):

Rear (with all the other jacks):

Top (with the heatsink outlet):

Bottom (with the mounting boss):

With the cover off, the inside looks like this:

The two rubber blocks glued to the hard drive bracket (carrier / sled / whatever) conceal the screws holding that side to the chassis. However, removing the blocks and the screws didn’t release the bracket, because it had what looked like a black adhesive layer below the screw flanges:

Gentle prying from the edge of the bracket eventually released it, showing that the black plastic was just an insulating layer. Below that, two thin foam strips had firmly affixed themselves to the PCB, despite not having any adhesive on that side:

With the bracket on the bench, installing the SSD went exactly as you’d expect and reinstalling the cover was, quite literally, a snap.