Clearly I never did my boy scout knot badge because my knots were rubbish.
This is why everyone should know how to tie this: The Fisherman's Knot
It's simple, strong, and easy to do.
Also, if you want to use bedsheets/curtains/blankets as a rope it would be best to fold them in half 3 to 5 times along the main axis so that they will hold more like rope. (that means they'll have 1/8 to 1/32 their normal width.)
I am absolutely no good at following these written instructions. I’ll have to find someone to show me in person.