I think the simplest design would be the classic, literal, 'ship model built in a bottle'. And with that, it's literally all about manual dexterity in gluing to

I think the simplest design would be the classic, literal, 'ship model built in a bottle'. And with that, it's literally all about manual dexterity in gluing together a model of a boat with all the parts glued on from the end of long tweezers and similar tools. In that case there's nothing 'impossible', it's just an incredibly tedious and painstaking process, and that's the only point of it.