Slatted Bed Base Typical of Pine Beds

Blossoming, thanks. The thing to go over the slats would have to be about three inches thick and quite rigid if it were going to lift the mattress enough over the slats.
From what Mollygo says about modern mattresses being heavy I think I will just have to keep the arrangement I have with slats, the thick mattress, and the thick topper which is light weight enough for me to lift the corners of.

My bed is a complicated affair as I have the top end raised up on bed blocks for gastric reflux. Raising the bed on blocks is so successful for stopping the reflux I want to continue with the blocks.

Mollygo, my main reason for having a four inch thick memory foam topper is so I can easily lift the corners of the topper to slip bedding underneath it.

I need a new topper, which is why I am exploring alternatives

Yes, I get what you mean.
Ours isn’t much of a dip to the slatted base, but even so, we usually stand at the end of the bed andpull the mattress away from the bed head and then slide the mattress topper elastic under the mattress. Then we add the fitted sheet before we push the mattress back into place.
Mattresses are so heavy nowadays. I can just about manage it by myself, but usually it’s a two person job.

It’s called a mattress underlay and they’re available on Amazon in different sizes.

My adjustable bed frame is much the same Caleo and MrB got a sort of non slip mat to go over the slats. I’m not sure what it’s called, but it does help with bed changing. I’ll see if I can find anything about it.