Hey man,
I know what your going through, and it is really tough. But here's some advice that I hope will help.
People think sampling is really easy, I mean, in theory, it is. Find an old sample, drop some drums + bass over it, and wah-la.. wrong.
It's hard working becoming a sample producer, but man once you start getting the hang of it, theres nothing like it.
The MAIN thing when it comes to sample production is PATIENCE. The more you listen, the more opportunities pop up for a dope sample. You've really gotta listen, and then re-listen.
Secondly, a lot of new producers (me included) get frustrated too easily and think, "Why can't I make a beat out of this sample?"
But what we don't realise is that you can't expect to make a dope beat out of any random track from your mums collection. Its gotta be something that jumps out at you, something that inspires you to turn it into a beat. This is such a key factor that a lot of people over look. Don't be put off because you can't make something sound hot straight off, its got to be a GOOD sample.
Thirdly, take the time to train your ear. You might notice around here (on the digging forum) that most of us are collectors. It comes with the territory of beat making. You start to really admire the artists, and after awhile you can tell whats gonna be hot and whats not, just by looking at the record, or checking out the credits on the back.
Listen, listen listen. Do your history, and just take it slow.
Fouth, Keep digging. Don't stop. You said your going through your mums mp3's if I'm correct? Why not invest in a ****ty turntable and a pre-amp or cheap dj mixer, and start digging your heart out. Raid those second hand stores and ****. I go nuts every time I walk into a used-goods store in another town. The more you dig, the more sounds you are going to have to work with, and this is what a lot of new guys forget/don't know. You've always gotta keep looking for that "wow" sample.
Hope this helps man.
P.S I don't know about the 6 second thing, but as someone said, try recording into another program such as Adobe Audition. That way you can do all your trimming/effects in there before exporting to FL.
And if your getting annoyed with FL, you might want to try Ableton Live (
www.ableton.com). I use it, and I think its perfect for sample-based production, but everyone has a preference.
Peace!
Maks