To use the onboard IDE of the Terriblefire cards you need to add the ehide.device, either using loadmodule after booting from an internal drive or you can build a custom ROM, if you have a 3.2.1 ROM this is super easy as there's (just) enough space to add it without removing anything or creating a 1Mb ROM.
loadrom "ROMs/Hyperion/3.2.1/A1200.47.102.rom" add "Components/TerribleFire/ehide IDE Driver 1.1 (18.6.21)/ehide.device" checksum saverom Kickstart.3.2.1.withehide
If you have a twin ROM system (e.g. A1200) and want to create files for burning to 27c400 eproms (e.g. you need to split/byteswap), then instead of "saverom" you can create a profile and save that instead;
romprofile 0 0 saveprofile 512 byteswap Kickstart.3.2.1.withehide
The romprofile 0 0 just adds two copies of the ROM "overburning" to fill the ROMs - you may get unexpected results if you only partially burn EPROMs.
This will create two files "Kickstart.3.2.1.withehide.0.bin" and "Kickstart.3.2.1.withehide.1.bin" for burning.