oh, I forgot to put in once you cover the top of your ff bait container with a fresh sheet of saran wrap.... make sure it's tight and put the jar/bait container in your freezer for a good 2 hours. That should be enough to stun the flies so they can't fly off.
Once they're frozen/stunned you can just take your finger and get the flies and dip them in the betta tank.
Make sure not to get the flies that are actually submerged in the wine/vinegar. The ones that are stuck to the side of the jar would be perfect. I use clear glasses about the length of my finger.
I hope you know apple seeds have traces of arsenic in them. I still like to chew up the seeds because they have a weird subtle but pleasant almond extract flavor.
You can use banana stems too, but sometimes worms hatch out of the stems. Pretty nasty stuff.