Here's a photo from a bit further back.

This is where a crows-foot wrench is one possible solution.

However, I strongly suggest that you have a tech from your gas provider do this. He will have a means of testing for leaks, be familiar with safety codes, and likely have a more optimal wrench for the task. And you won't have to worry about your insurance company declaring that any fire or explosion was your fault.

As a wag on a code inspector forum once put it: "The purpose of code inspection is to reduce the income of lawyers." Gas company techs are responsible for meeting code. Lawyers will cost more than the tech. So, unless this stove is outdoors in a desert, please take the safe path and leave something as dangerous as a potential gas leak to those trained to deal with it.

kas

Crow foot wrench and a long handled adapter for your ratchet.

Normally you would put on a longer pipe and then your flex adapter.

I'm seeing a couple things in your photo that look puzzling.
If this range is to sit back against a wall, the flex cannot come out the back like that. If that panel just below the flex is removable by that one screw, then remove it and put a 90* fitting on the range, then attach the flex so it exits downward behind the panel allowing the range to fit against the wall....Just a thought

Kaseki, that is a great idea! I will contact the gas company and have them take care of it. Our gas company has really great customer service. They will probably have the crows foot wrench (I'd never even heard of that, neither had DH) but just in case I will get one so they don't waste a trip.

Ctycdm, the flex hose actually feeds down a gap behind the panel there so the range can sit flush against the wall, we just didn't bother for the photo. That was probably a bit misleading, sorry! The problem with trying to add a 90* fitting is the same as connecting the flex hose, I just can't get a wrench back there, but I think the suggested crows foot wrench will do the trick.

Thanks for the help and suggestions everyone!!

OK that makes sense now! Also a sink basin wrench will work as well, and it's a handy thing to have around the house anyway!
Good luck with your hook up, and happy cooking!

Chantel, I agree with the suggestion to contact a professional, also, I looked at the installation instructions, and they were pretty weak. I had an older Viking, and you reached the nut to tighten from above, not the back. That is the burner assembly lifted off, and so you could reach that place from the top. I don't know if they changed this by going to sealed burners -the use and care manual does not show anything about whether the burner assembly comes out.