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? I want to get started on this, but the back panel is bowed a bit. I’ve weighted it down overnight to no avail.
Heat and THEN weight? I donno
How do I get it flat?

Here it is for eye candy:;)
Katalox



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I’m realizing I have a lot of questions going on today ha


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It looks like it is flat-sawn, not quartered (which is why the figure looks so nice!). That board wants to bend a bit, and you can see it in both book-matched halves. If you are going to use this stuff you need to accept that it does not want to lie flat, which is challenging but not impossible. By the time you make it thinner, and then brace it, you will likely be able to tame it. I will offer a couple of thoughts - but I am a relative novice so ignore me if a more authoritative voice contradicts:
1. It might join better if you jointed the outside edges. Bookmatched panels can go either way - just ignore the outline that has been drawn on it.
2. It is probably futile to try to get it perfectly flat now. Weigh/clamp it down on your shooting board and shoot a joint that works when it is flat. Then glue it with weight on it to mate those faces well. Then thin it to your build specifications and you will find it gets floppier. Then brace it and see what you end up with.
3. Be careful to do all of this at RH no higher than about 45%. If you let that board get humid it will bend more.
4. If all fails that wood will make some nice headstock faceplates and bindings.

There are some ideas in these past threads:

https://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=52988&hilit=flatten
https://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=52081&hilit=flatten

You may be able to find some other threads here on the topic since it seems that builders run into this fairly often.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Join it, thin it, brace it. Once you add it to the rims it’ll be fine.

soak it water
stack it between several sheets of newspaper all around, same amount of paper on the bottom, middle and top, place it between 2 flat boards with a heavy weight on it.
Change the news paper daily.
in a couple of weeks you should be pretty flat.
The goal is to get the wood wet then dry it evenly with the weight and newspaper.
unfortunately, I know this works

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Jim Watts
http://jameswattsguitars.com

Unfortunately I have to deal with this almost every day. I've sold many hundreds sets of koa over the years and each set requires a photo. To show the actual wood color, I spray the wood with water before taking the pic. I'm usually taking a few photos, and by the time I'm done, every set will be warped. I've tried a few other chemicals, like Naptha, alcohol, etc,. but nothing works as good as plain old water. When I'm done I spray both sides of every piece in the set with water and dead stack it on my shop dry room cement floor with a long board and weight on top. Sides on sides and backs on backs. You don't need lot of weight. The stack can be 1 set or 5 sets high. It does not matter. I've never had a set not be flat the next day. If the wood warps again later, I never sell it or use it myself. I discard it. I am not in favor of trying to force wood to stay flat. IMO, much better to use stable wood in the first place. Good luck with your projects.-Bob

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“ The meaning of life is to find your gift and the purpose of life is to give it away” Pablo Picasso

When I run into this, I will lightly spritz the concave side and flatten with heavy boards. Then, go work on something else for a while.