All you need to do is participate in the Nature Day event, and speak with Tom Nook. He'll send you the recipe for doing so!
To craft them, you'll need:
x10 clump of weeds
x5 tree branches
x2 stone
I believe it makes 10 of them!
To craft them, you'll need:
x10 clump of weeds
x5 tree branches
x2 stone
I believe it makes 10 of them!