Please be careful when you purchase felt for applique. Make sure you purchase real wool fabric. Some shops sell "felt " fabric for wool applique that is not wool or a has a low percentage of wool. The issue is that the blended fiber is man-made and will scorch when ironed at wool settings. Also some felt squares (usually man-made fiber) can be very thin.
The lower grade felt can be useful in some projects. Just make sure you get what you want.