Sorry to hear the plastic bottle did not work. I have a problem with flies on my porch. Maybe they are attracted to the smelly shoes & sandals. The other day I placed 2 sticky fly mats on the porch by the shoes, which I bought at Handyman Hardware. Caught lots of flies. The wind blew over the sticky matts so I placed the corner of the mat under a leg of porch furniture -- no problem with wind since.

 

I am planning on cutting an empty plastic soda bottle in half and making a homemade fly trap out of it. The below link includes that option (and other options).

Homemade Fly Traps on Pinterest | Homemade Fly Repellant, Natural Fly Repellant and Keep Flies Away

 

Three ideas from pinterest: in a small clear sandwich bag or ziploc fill halfway with water and add 4 or 5 pennies, hang this near the door or use outdoors too. At the table set a clear glass half filled with water and add 4 or 5 pennies. In a small bowl place half a lemon and stick it full of cloves, lasts a few days. If your American friends do not have pennies, Canadian friends may have pennies, maybe the 10 centavos will work. Good luck, be fly free.