Find the file named lift.exe in the game files (in "C:\Program Files (x86)\Steam\steamapps\common\Portal Stories VR" by default) and perform the following steps:

1. Right-click the file and select properties
2. Navigate to the compatibility tab and enable the app to run in compatibility mode for Windows 7
3. Apply the changes

After that, find the file named Lift-Win64-Shipping.exe in the game files (in "C:\Program Files (x86)\Steam\steamapps\common\Portal Stories VR\Lift\Binaries\Win64" by default) and perform the exact same steps as on the first file.

After making the changes to the files, perform the following steps to begin running the game:

1. Open SteamVR manually from the steam application
2. Run the file named "Lift-Win64-Shipping.exe"

Step 2 should open the game like normal. I've read that running the game from the steam application undoes the changes made to the files and you'll spawn in the floor again, but I haven't tried it so I'm not sure.

These are the steps I followed to play the game myself so I know they work at least for me. Thank you to the people in the discussion linked above for providing the solution to me initially.