How to Create Custom Firmware IPSW with RedSn0w

The new Redsn0w, like PwageTool and Sn0wbreeze, lets you create custom firmware to preserve iPhone baseband. You can create custom IPSW firmware with RedSn0w with preserved baseband so you may unlock with UltraSn0w or Gevey SIM. For those unfamiliar, a custom firmware, unlike stock firmware, preserves your iPhone baseband. With a preserved baseband you can unlock your iPhone either using