Use 95-100% Wool Felt. This is a good idea for the laser cutter in order to avoid the release of toxins into the air, but it’s also a good idea in general, as the material quality of 100% wool felt makes a huge difference in any project.
There are two types of high-grade wool felt you can buy. Industrial/SAE felt is fabricated to standards set by the Society of Automotive Engineers and comes in cream (new wool) and grey (a mottled recycling of old wool and other materials). There is also 100% wool felt that is usually sold for doll making which comes in a multitude of colors. Stick with the plant-based dyes. Don’t get the craft-store felt — that’s mostly acrylic and is just really low quality in general.