For a non-native speaker, even the word "foreshortening" wasn't immediately intuitive, so I'm going to post its definition for posterity:
foreshorten: to shorten by proportionately contracting in the direction of depth so that an illusion of projection or extension in space is obtained (Merriam-Webster)
The "Drawing on the Right Side of the Brain" book by Betty Edwards makes you do an exercise of portraying your hand, foreshortened.
First, the book asks you to mark it on a piece of plastic called "viewfinder" (I'm using the one included in the workbook, but it's really something that can be made at home) like this:
It already looks pretty good! By drawing the trace on the viewfinder, you are not tricked by the preconceptions on what a hand should look like, so you can really draw it as it looks.
Then, you have to draw your hand on paper, using your real hand as a reference (in the same pose as the viewfinder mark), with the possibility of looking at the viewfinder too.
The hand represented in the viewfinder above came up like this:
I'm pretty satisfied with the result. The next step would be to do it without a viewfinder (or as the author puts it, use an "imaginary" one).
Bonus content: I've actually done another pose before this drawing, which came up quite decent too but I didn't have the viewfinder photo of that so I'm just posting it at the bottom here:
