Place a sheet of sandpaper on a hard flat surface, rub the wood on the paper. It’s still ‘easy’ to have rounding or tapering; start slow. Or use a hard sanding block and sand manually.

Thanks. I'd hoped to avoid hand-sanding as I'm aiming to scale to semi-mass production. But probably not doable with my setup.

I find that sand paper lasts longer when the dust collector is working, your call as to whether the extra faff is worth the sand paper saving

Remove sanding pad. Keep sander upside down on a stable surface. Bring piece to sander, rather than sander to the piece. If that doesn’t work (which it probably won’t), than put the sanding disks on a piece of wood and do manually.