JAWS has this functionality built in. The feature is called screen curtain and is accessed by layered keystrokes. If I recall correctly it would be JAWS key + space, then F11.

TLDR: Turn off sleep-on-close, plugin keyboard, close laptop lid, give laptop airflow, enjoy.

Reposted from /r/windows10 in case someone comes across this sub later or uses Reddit without cross-posting support.

I've taken to carrying an external keyboard around, connected to a laptop via USB. The laptop goes onto a table, or leans against the side of the chair I'm in. This typically provides adequate airflow. To let this work, you have to turn off the sleep-on-lid-close feature in the power section of the windows control panel. You could also use a wireless keyboard if that's your thing.
Edit: While the lid is closed, the screen is disabled, from what I understand. I failed to explain that crucial point earlier.

I have yet to find any feature in Windows to continuously disable the monitor.
There is an internal programming function to disable the screen when there's no activity, but obviously that won't work for your use-case (or mine).
This includes programming and Windows's internal API's.
That being said, I would love if anyone could offer another suggestion.