But be warned: You may want to avoid Thai mats filled with Kapok fibers. While the organic material is considered a cushy substitute for goose down, it’s highly flammable. While you can use any fabric you please, for the best comfort, stick to 100-percent prewashed, organic cotton. Stuffing the mattress with organic buckwheat hulls will naturally combat dust mites. The hulls are also fire-resistant and biodegradable.