I learned about how to flip textbooks from reading :
Book Sourcing Secrets: Every Source of Cheap Books to Sell for Huge Profits on Amazon
In this video I give you a quick overview of the process that the book explains.
The author of the book also just created a software program to make this easier ( for like $97 a month..yikes!) but you can do this without any software. My explanation probably doesn’t give all the details, book if it is something that clicks with you, you might want to read the book yourself
Here is a post he did on textbooks