Yup that's what I did. I just cut a 12 foot extension cord and stripped the wires back, split them, ran them through a small hole on the back top, and attached them to the hook ups on the back of the fixture. Did your fixture come with short screws? Actually mine came with screws for metal, and I had to buy short screws for wood separately. My fixture had holes to put the screws through. I just got a screw long enough to hold it on, but not go through the top. The fixture I bought had 4 sets of holes for screws two for large screw that you would turn the fixture a bit to set them on the screws, and two small holes for screws just to go through. I was able to pull the wire through one of the screw holes to let it sit flush with the top. If your fixture can't be screwed on which would be really odd you could get some strong adhesive and attach it like that. If you can screw it but you have no way to get the wire out from the back of the fixture without having a lopsided fixture, what you can do is just cut a circle of wood the same size as the fixture base is round with a small piece cut out shaped like the letter C and run the wire through the opening and allowing the fixture to lay flat. I hope you understood that? Ask the people at home depot or the store you use for the proper adhesive if you need to go that route, but you should not have too.. Any more questions just ask.
bad pic of the fixture but you'll get the idea

Pic of Lucky Buddy in his new enclosure. Sorry had to add this pic too. Had to show of my Buddy.

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Mystical Dragons