Hacker Help: How to hack my slip covers to NOT do this??

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photo2 723292
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Materials: dunno, help me!!

Description: I love my IKEA sofa, but I do not love how the slip covers tend to….uh…slip so easily on the cushion.

Friends of mine who also have furniture from IKEA are also frustrated by this.

Anyone have a solution?

Thanks!

~ Steven

Jules Yap