Load up your Fruity DX10 in Flstudio . Pick the Upright Bass2 preset . Set the init to 0 in modulation 1 .Do the same with the TIME button .
Now set the Sustain to about 15% , or just set it to a level that sounds good to you . Tweak the Attack , Decay and Release in the amplitude area , i usually set the att to 0 Decay to 100 and release to 0 . But you can do it just the way you like it
Should look something like this :

Now load up your 3xOsc to create a sub bass to make it sound fuller . Set the Osc2 and Osc3 volumes to the max.

Now equalize it the way it sounds good to you (I suck with equalizers so its useless to hear any pointers from me

Add some distortion if you want . That should be it

I Hope this "tutorial" helps you guys

Take care .