single word that means which can be constructed at home

What is the word that means “that which can be fixed up at home”?

For example, I buy parts from a store, bring the parts home, and then can construct the thing out of those parts by myself. What is the word that means such an object, one that can be made at home in a do-it-yourself style?

I don't think there is a single word, hence the popularity of the acronym DIY. The closest term I can think of is self-assembly.

Coming from the German word 'Bausatz' which should be the one you mean, I would translate this by 'kit' if you really need just one word. If two words are still reasonable I'd use 'construction kit' or 'building kit'.

An object which has been made at home can be called homemade. While this term is often used for cooking, it is used for many other things.

If someone were to ask you where you got that "thing", you can tell them they can make it themselves at home; it's homemade.

A synonym of homemade is homebuilt (alternatively home-built or home built). There are many references to things that can be constructed at home including homebuilt aircraft, cars, guitars, and homebuilt machines in general.

Another term that is not as widely used is homebrew. The term originates in brewing beer or spirits at home, but has been adopted for use in other fields, including electronics projects (here and here), computers, car projects, and a homebrew nuclear reactor.

DIY or do-it-yourself has become a very common term in the U.S., contrary to some comments here. We have the DIY Network, part of Home and Garden TV, which has become an institution among DIYers, handymen (and women), homemakers, and homebrewers.

To make something from readily available materials is to improvise. Improvising doesn't have to be done at home. It can be done anywhere. Here is a YouTube video example of improvising.