how to creating a secure flash drive

Use Disk Utility to create an encrypted disc image in which you can store secure files. You can also buy encrypted flash drives.

It's easier to have the drive encrypt itself in hardware.

http://www.ironprotector.com/

Setting up an encrypted disk image is a no brainer. I don't know how much these hardened flash drives cost. It may be they are no more expensive than the usual suspects, but I would imagine they cost more and being restricted to these will limit choice.

http://support.apple.com/kb/HT1578

A flash drive is meant to be portable, if it encrypts in hardware on the device itself, then one can take it to any machine and use it.

There are also other benefits, like secure web browsing etc.

Sounds good if that's what the OP needs.

Note that the OP is using Snow Leopard. Full disk encryption is not available in Snow Leopard as it is in Lion and Mountain Lion unless third-party software is involved.

Talking about a hardware based self encrypting external Iron Key USB thumb drive, not Filevault 1 or 2. 😀

OS X's FV encryption scheme isn't used at all, which makes it ideal for taking it to different machines.

I had already made that suggestion before you joined the fray.