Why You're Failing at foot stand

http://trevorqbsu966.edublogs.org/2019/07/09/addicted-to-dr-foot-desk-foot-rest-us-too-6-reasons-we-just-cant-stop/

I bought this to put under my desk to rest my feet to support my back.. the rest slides back and forth- will not stay in place. It adds pressure to my back and makes it worse. Not a good footrest.