There must be a tutorial.
You are right they are stabalized with a lightweight fusible stabalizer. It is generally used in tailoring. Someone else will know it's name. it stretches one way and is stable the other. You put the stable direction on the stretch direction of the T shirt. The stretchy direction goes on the stable direction of the T shirt. Then the whole area is stable and you can cut out your blocks. You can put two small areas or even three or four small areas together to create one block. They are some of the most treasured quilts that I have ever seen.