Normally on my ribbon door plaques I attach the ribbon to the back of the plaque. But as you can see from the above sample photos of my two-sided plaques I attach the ribbons to the sides of each plaque. They simply just need to be lifted off the door knob, the hook or whatever you are hanging the sign from and then flipped around.
In the one sample photo you can see it's a but different. By the customer's request I drilled a hole in the plaque and hung it from a ribbon in the center of the plaque.