Fleece & coroplast???

Hi Ferrickhead, you need to use something absorbent under the fleece. I've found mattress pads to be the best thing to put underneath. Some people use towels but I find it gets smelly after 2 days with towels so I definately recommend mattress pads and fleece. This is a good thread about fleece https://www.guineapigcages.com/forum/bedding/21568-fleece-project-study.html
Also have a look at the other sticky thread in the bedding section about different types of fleece.

I found coroplast really easily by phoning all my local sign makers and opting for the cheapest. They all sell it.

Fleece itself isn't absorbant. The reason many use fleece is because it "wicks" or pulls moisture through itself to whatever is under it. Thus you must have something absorbable underneath it. There have been a couple members who've used cloth diapers under fleece but I really don't know how much success they've had with that method. Many use mattress or crib pads under. Some use towels. Some use newspaper but newspaper would need to be changed on a daily basis vs. mattress/crib pads that would only need changed once per week when you do a full cage cleaning.

The other thing with fleece is that it needs to be spot cleaned at least once daily to pick up the poos.

There are downfalls to fleece in such that hay sticks to it so one needs to get creative with how to put in hay when using fleece.