Create a products page just for these specific products, and put it in the unlinked section (you'll have to keep it active, not disable it).... then, you'd have to do what you said.. add text & products to a blank page.
You can keep a separate product page for other products you may have, aside from these special products that get added to a box.
I assume you're creating something like a "build your own box" feature...
First section could perhaps be "box size", and you'd have a "box" product with size variations with different price points... Then the next section could perhaps be "Beauty products", and you could add different beauty products to add to the box... etc.
The user would just be filling up their cart with your build-a-box items....
You'd have to differentiate your build-a-box products (perhaps in the SKU or Title) from your regular products, so you'd know which items go into the box, and which items are just ordered separately.
Hope this helps!