Start with core and decorate with stuff.
Specifically, use a box generator to generate the core structure. From there, you can delete parts of the box and join boxes together to create a more complex shape. Or you can add bits to the box, as needed.
For a caddy, I might start with the box generator in Inkscape and create a box that is, say, 6" x 6" with 2 internal dividers and an open top. That’ll give you 4 3" x 3" compartments. From there, you can extend the “tops” of one of the dividers and then cut out a handle. And make a nice round shape at the top.
You can also generate a box, then cut the tabs and past said tabs on a different shape, if you want. You can also cut the tab holes from a generated box and paste them on anything else to make a tab+hole type connector!
I’d also recommend starting with a very basic box that has at least one divider. Dial in that kerf and thickness with whatever material you are targeting. I’ve had great luck dialing in the kerf to the point where I need no glue at all to create a box that will not come apart without near destructive force.