Flat, Peace
If you want to dry your horns you need to lay them flat. If they aren't flat they'll always be a little damp somewhere and you'll never have a moment's peace.
Imagine carefully taking off your horns and laying them flat on a paper towel. You have to smooth them out so they're as flat as possible.
へい, ひょう, びょう
たい, ひら
None
Being flat isn't enough, so you cover the whole thing in hay (へい). Hay absorbs water, so you add a flat layer of it.
Imagine carefully laying a flat layer of hay on top of your flat horns. You feel really at peace and... you're tired now. You decided to lie on top of the hay and take a nap while you wait for your horns to dry.