Put it on upside down
This worked perfectly for me with only one suggestion for the rest of you. The way the item is pictured shows a black strap which would go around the back of the sofa to hold the top part of the slipcover in place. I didn't notice this when I ordered or I would have opted for something else as my sofa is white and the strap really stands out. Also the slip cover wasn't staying in place well until I decided to flip it upside down. The part of the cover that goes on the back upright side of the sofa with the strap is now on the seat cushions with the strap running underneath of the cushions. My sofa has three cushions for the back of the sofa that are unattached. I removed the cushions and placed what should be the part of the cover to be sat on over the bare back and let it fall behind the sofa. For extra measure, I wedged a tension rod between the back of the cushions and the upright backrest portion of the sofa and then replaced the back cushions. I also let some of the cover hang down the front and tucked underneath the seat cushions. It's been three weeks and the cover hasn't budged. I haven't once straightened it out. If your sofa doesn't have removeable backrest cushions, you could put the cover over those cushions, but you would really need the tension rod. It wasn't necessary for me to try it that way, so I don't know if it is as perfect a solution as with my removable cushions, but certainly worth a try.