Collect and prep the bodies
Sounds gruesome, I know! If you aren't a bug person then this might not be for you. Let someone more buggy do this part for you!
Pick the right kind of resin, you want it to be nice and clear.
mix and pour
Only mix a little resin at a time and pour quickly because it sets up fast!
Allow to cure completely before de-molding your resin insect.
Pop bubbles with a heat gun. If you have a lot of bubbles, coat the insect in resin and allow to dry before placing it in the mold.
Using a tray instead of a mold
do multiple pours
Do shallow pours and allow to dry between pours. The insects will stay at the bottom and you will be able to get rid of the bubbles easier.