Primitive Archer

Here's a post from my blog showing how I do it.
It can help to take off any excess from the edges with a band saw first, similar to cuts 1 & 2 in this sketch (which was to illustrate chopping out the belly from a half log, but hopefully you get the idea)
https://bowyersdiary.blogspot.com/2014/11/bamboo-backing-build-along.html
Del

It is almost always twisted....that and the groups of pin knots are what you need to avoid.
Often its best to get billets and splice them.
It won't straighten very well either.....
Probably firewood.

Depends a bit on your height, too.  Start long, you can always pike the limbs.
Hawkdancer

So clean and dare I say elegant.  Strong work.

The easiest method involves the use of power tools. I trace on the profile of the belly onto the bamboo and then cut it out on the bandsaw. I then flip it on its side and cut the thickness profile down a ways.  I then use a belt sander to thin it and flatten it. Not the most primitive methods, and I know it can be done with hand tools, but I don’t have the patience for that, especially when the power tools are staring at me.