Building a box around it will work, but you do need to make sure there is enough openings to allow free air flow.
Hi Sue, is this for an indoor unit or outdoor air conditioner? Here is a post on making a screen to hide it outside:
Window air conditioner or central air?
The outside unit can be surrounded with latticework or shrubs.
Hi Sue: Hopefully this is on the ground:) If so, you can put up fencing or bushes. If it's on the house window, you can paint it to match the house or paint it and attach some stickers that look like vines or flowers. Good luck
I saved this project for my "to do" list https://www.hometalk.com/30370234/removable
Some ideas for you: