Go to Ace Hardware on 98 in PCB, get several beach balls, black spray paint and stick-um. Paint the balls, spray on stick-um and hand the balls in the yard. The flies are attracted to the dark color and then stick to the balls.
My family has found that it's just as effective to get the cheap, black plastic garden pots and spray the Tanglefoot (adherent) onto that and hang. Same effect, a lot less work! They need to be hanging, though, because the movement attracts them. Good luck!
and also spray YOURSELF with bug band, available at the gulf place pharmacy and on amazon. it is sort of a lotion spray, but very effective. smells like duncan hines yellow cake batter!