056 Here you go. Just work with whatever you have, rip a board out of a chunk or trim down a sapling. Measure the width of the board then cut your notch. If it does not feel safe then drive a wedge in under it.
I think Madsens can still get the tips, then just shape a good thick plank and start practicing cutting the notches. I've only had to use them a handful of times but they were needed badly.