Software
There are those that use a program called LittleWriter to write games to the cartridges. However, some people (especially people with older computers) use other software to write games to the cartridge. An example of this software is X-ROM Frontend by DanSoft Australia.
Some flash cartridges use specialized software designed for the specific cartridge, such as Power Writer and USB Writer software for the Flash2Advance Ultra cartridges. This presents several conflicts in regard to homebrew, as Power Writer uses a large database for proper naming and saving of games. ROMs that are not in the database (such as emulators or any other GBA homebrew) are prone to saving issues, and editing the database manually is difficult and involves the use of a hex editor. Such cartridges often have a proprietary interface, making it difficult or impossible to use operating systems other than Microsoft Windows for writing to the cartridge with a few exceptions.
Read more about this topic: Game Boy Advance Flash Cartridge