For reference, I have next to zero knowledge of building electronics. I've replaced the joysticks on two Nintendo joycons (which I actually found pretty fun), and that's it. I also have no experience with 3D printing or designing specific products.

I am also sick of touch screen keyboards on phones, do not like any of of the phones that do have keys or the Clicks phone case (why is it on the BOTTOM—), and currently have a lot of free time.

So my question to you: how would I go about designing my own slide out case with its own keyboard?

Because that is my ideal solution at this point. And in fact, it turns out someone DID make a 3D printed "slider terminal" this year. Except it's for the Note 10 (I have a Galaxy S9), and seems to be used as a full-fledged replacement for a desktop experience with a trackpad. That's neat and will probably appeal to a lot of people here, but personally, I just need physical keys.

Along with the keyboard used for that terminal, I also found this other tiny keyboard which doesn't have the trackpad and is about the same dimensions as my Galaxy S9. Actually I found that first and was trying to figure out if there were any cases that could store and pop that out. The biggest issue is that it would cover my camera except maybe when it's slid out, but screw it, I want a damn physical keyboard.

I do have access to 3D printers (yay public libraries!) and I'm willing to learn Blender in order to make this thing. I just need advice on where to begin and how to tackle this. In particular, I have no clue how to go about the slide out part. I feel like I should be able to figure out how to make a case that fits the dimensions of my phone and the keyboard fairly easily, but no idea where to begin with researching the sliding component.

Besides that, I also know that I'm not alone here in my frustrations with phone keyboards, so I'm hoping we can pool together ideas on how to do this. As far as I can tell there's not really a "one size fits all" solution that would work for all phones (well, except perhaps a foldable case instead of slide-out), but maybe we can at least share decent starting points for people to design their own. For instance, the slider terminal uses a keyboard that came with a remote, and it would never have occurred to me that could be used for this sort of project. And there are a lot of potential workarounds for the camera placements, so Person A may have an idea that doesn't work well for them, but does work better for Person B than their own original idea.

So yeah. Advice, ideas and general brainstorming are welcome!