By far the most elegant is to use the Melas Waveform Editor* which allows you to assemble the sounds you'd like by simply dragging and dropping them into a MOXF library, create a .X6A file. Then you can format the FLASH BOARD and install that newly created file onto your Flash Board.
*Melas Waveform Editor is a third party program for Windows or Macintosh, that lets you create and manage data on your computer.
If you are doing it with just the MOXF hardware there are two approaches:
Install the data to the MOXF and go through all Banks making note of which Voices you wish to keep.
Then you can either
1) format the Board and then Load just the ones you wish to keep (using the Load "voice" or Load "1bank voice" File Type).
2) delete the ones you don't wish to keep
Either method is a bit time consuming but the MOXF will do most of the heavy lifting- you simply make the selections and press the buttons. Which you choose will be determined by how many you wish to keep versus those you wish to eliminate. If you are only eliminating a few opt for method two. If you only wish to keep a few opt for method one.