I can't personally recommend any group in particular because it's the individuals within the group you would be dealing with and, of course, without knowing them personally, I couldn't recommend them as 100% trustworthy. I would suggest that you structure the position you have in a way that you can check that the work you require is done to your satisfaction and then make payment.
One other platform is the peopeperhour network. That's a freelance network and I have no doubt you will be able to hire someone there if you post the position. That's one of my favourite go-to spots when I need anything done and happy to recommend that. Just post the position as available and people will submit their quotes to do the job you require or you can set the price you want to pay and receive applicants.
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