.... it's been a /very/ long time since I've used bales of hay to mulch
with.

My question is, what sort of area should I expect to cover per bale?

I used to peel off a 'slab' about 2-3" thick to mulch any given spot, if
that's any indication.

I'll most likely get the older/smaller bales rather than the big round
type - depending on cost and availability - but if anyone can give me
average coverage figures for either or both types, I'd very much
appreciate it.

Cheers