I will freely admit that the Nintendo Labo kits are beyond me. However, quite a few people are thrilled with the cardboard perhipherals for the Nintendo Switch. However, one problem with them is the lack of spare parts. However, the Labo blueprint patterns are now available online through Nintendo (for free, even), however the Labo does need more than just cardboard to work, so you can't quite build your own.
In order to control the Joy-Con as a fishing rod or an RC car, you're going to need the software to do so, which simple cardboard just can't get you. Sadly enough, you cannot craft your way into getting a free Labo. I know, I know. The world is not fair.
The patterns are designed to be blueprints for replacement parts because the Labo is designed for children and children are great at destroying cardboard. So if you need spare parts because you busted yours or wore them out, Nintendo is at least a bit merciful.
And, as Polygon indicates in their report on the spare parts, "The .pdfs are also a tip-off for how intricate these Labo creations are and how much work may be necessary for them."