How to create multipack of multipacks?

I want to create a multipack that itself is created of multipacks.

For instance:
We have a multipack - 6 x 341mL bottles in a cardboard carton.
We also sell “flats” of that product - four six-packs on a cardboard flat tray.

How do you assemble a multipack that consists of a multipack?
The reason we want to do this is so that we can auto-allocate or auto-disassemble into individual six-packs as required.

Is there a way to do this?

You can create both multipacks (4X6 & 24s - I can’t have both?), but Breww won’t inherently know that they’re packaged differently. It will just think that you have two products with exactly the same beer components - it won’t know that one is essentially a multipack of multipacks. However, being different products, you can add different stock items to each product, so you could add ‘flats’ specific stock items like the cardboard flat tray to one product, and not the other product.
Does this solve it for you?

No it doesn’t solve it. I can create a multipack of all the required components, bottles, cartons, labels and the tray. Sure.
And I can create a sixpack of the same beer, no problem.
But an assemblage of the two I don’t see a way to do it.

The issue at hand is that if I package to the flat tray product I can’t then disassemble it into four six packs. Breww tries to disassemble it into individual bottles.

To disassemble a tray into 4 x 6-packs you would have to go via individual bottles. If you leave everything up to auto-assign, the two-step assembly should happen automatically and you needn’t worry that it went via single bottles. You might have some singles left over if the quantities didn’t match up, but these can then be used in the next auto-assign. The stock items, like the tray etc, should work out if I’m understanding their use in your situation.
Alternatively, you could create the 6-pack as its own container type, then the 24-pack would just be four of these container types. This would only work if the 6-pack itself was never broken down into singles (or rarely, as there would be a workaround using stock adjustments).