How do you "felt" a project?

This pattern and others I have seen calls for sewing a potholder with felt?? I pasted the link below. What type of felt? Those square ones from crafts shop??

Thank you.

“Felting” is drastically shrinking a wool knitted item. It has to be made of 100 non-bleached, non-superwash wool for best results (other natural animal fibers felt also).

The piece is usually knit very loosely and then washed in hot water with lots of agitation so the fibers rub against each other. This causes the little hairs to catch on each other and the whole thing shrinks and thickens.

No felt required.

It’s amazing how much things can shrink. Many of us have made clog slippers that are felted. They look like they’d fit Shrek before they go in the washer!

Thanks for the tip!1

I always put the item(s) in a laundry bag because some wools get very fuzzy! Also I throw a pair of jeans in to help agitation and use the medium level water unless it’s a very large project.

Btw… Not all wools felt the same. Some don’t felt as much as others. I check every ten minutes because I can control the felting process and shape the the item if it needs it… Like bags and slippers.

Oh okay. I thought I needed to buy felting material or something and sew it in. Thanks for your help.