There are many different materials called *felt*
It depends on what. Felt you are considering. The acrylic craft felt kids use in school, comes in many colors, usually in 12" x 9" rectangles.can not be ironed, or washed- people use it for lots of crafts. Wool felt is washable and can be ironed. I've not seen polyester felt but would think it would be a lot like fleece, washable, iron with cool iron if needed but probably wouldn't need ironing. If its a walhanging experiment & use what you like.