I've tried a few methods to preserve flowers and one that works pretty well is air drying, it's really simple and doesn't require any special equipment, just hang the flowers upside down in a warm dry place. Another method is using silica gel, you can buy it online or at craft stores, just place the flowers in a container with the gel and seal it, this method helps to absorb the moisture and preserve the flowers. I've also heard of using glycerin, it helps to keep the flowers flexible and preserve their color, you can buy glycerin at pharmacies or online, just mix it with water and soak the flowers in it.