I purchased a Silicon baking tray liner which is pink and looks to be similar to the Supreme Slider.
I have cut a small opening just like the slider. It stays in place just like the slider and instead of A$40.00 it only
cost me $5.00 and is the same size as the slider.
I also use a Black Teflon sheet that can be used on an oventray/BBQ ($5.00) instead of the expensive applique mat, it works just the same for less money.
Both the above items have been bought at the Dollar Shops, Reject or Crazy Clarks here - but I am sure you would have the equivalent. I have never used silicon spray.
These work for me.