Silly question: Are they boots or could you just do them like legwarmers? Like... make a huge leaf shape to wrap around your calf, and then tie the cord/rope/whatever around it? Then you could make the slippers and wear matching socks to cover whatever bit of your ankle shows..
Or you could use knee-high socks, paint them, and just add fabric on top to get that.. torn leafy-type look. Actually yea, I vote for that idea rather than the first one I had.
And actually I don't think you really need to worry about leaf-type fabric. It looks like you can just use splotchy-green fabric. Then you can paint veins on, because it's not little leaves, each piece is one or two big leaves, and wouldn't require a huge amount of paint. Well.. not big considering she's like three inches tall but.. big in scale...
Upcoming Con: Anime Boston 2014
Sakura - Cardcaptors
Roxas - Kingdom Hearts 2
Cloud - Final Fantasy 7: Advent Children