Board: Old skateboard (I’ve found these on the street, should be easy to find in a few yard sales), cutting board (if you’ve a side you don’t use for food preparation and are good about cleaning or use a towel to insulate), cut off part of a 2x4
Pivot: Rolling pin, small rocks (though not pebbles)
Interesting prospect. I don’t think I’ve got any boards or rubber balls lying around, but will keep an eye out for something to jury-rig.
Other options:
Board: Old skateboard (I’ve found these on the street, should be easy to find in a few yard sales), cutting board (if you’ve a side you don’t use for food preparation and are good about cleaning or use a towel to insulate), cut off part of a 2x4
Pivot: Rolling pin, small rocks (though not pebbles)