EZ-Flash USA Forum

It has been known for a while but was not mentioned as much as it could be primarily as most people just used the inbuilt loader. To this end do not use any DS slot device to write to the NOR or PSRAM or you risk overwriting the bootloader.
There is no technical reason why it should not work but the EZ3 and so EZ4 boot/setup procedure is not entirely trivial (various pieces of memory get remapped to various places- see the EZ3 SDK files/sdkv1.1.zip if you are curious) and most devices lack proper support for it.

If you have done so and caused troubles for yourself (typically white screens or crashing in the loader) there are methods and tools to try rewriting the loader
The first option is simply to try updating the loader (putting ezfla_up.bin on the top directory of the card and holding R).

A standalone tool to attempt rewriting the loader
http://filetrip.net/nds-downloads/flash ... 27302.html
A full collection of EZ4 loaders for each cart save the EZ4 lite compact. If you have your own try that first though (at this point it is uncertain if things changed between the different revisions of the same model).
http://filetrip.net/nds-downloads/flash ... 27581.html