Wayne Boatwright said:

Sander, thanks for your reply and suggestion. I would prefer a mat
between 10 and 11 inches in diameter. One goal in adding this to the
turntable is to prevent slippage between the turntable and record, as
this has been a problem. I'm assuming cork, rubber, or a thinner foam
mat would solve this.

Apart from the suggestion by mr. Richman, you could try to experiment
with different kinds of mats.
Most commercial turntables are fitted with a simple rubber mat, but
one of the most important requirements is that the mat is flat, or a
little concave..
Then, when adding a record clamp, the record is kept firmply in place
to the mat.
All this is about supressing and/or absorbing resonances.

The main goal of the mat is to eliminate resonance of the record,
since every movement of the needle is represented as an electrical
signal at the cartridge's output.

Some brands (e.g. Linn) use a thin flannel or felt mat, which has a
different "sound" from a rubber mat.
It's about selecting the one that fits your needs.
At one point in my quest for "better sound", I've even used an acrylic
mat. It was said that the resonance characteristics of such a mat were
comparable to those in a vinyl record.
The "sound" of this mat somehow didn't appeal to me, apart from the
risk of slipping and damaging the record.

I now use a homebrew combination mat of cork at the platter side and
thin rubber at the record's side. In my system, I found this to be the
most satisfying kind of mat.

--
Sander deWaal
Vacuum Audio Consultancy