I got scaffolding poles, an old car tyre, and a boat fender to make a free-standing punch bag.
I put the tyre down flat on the ground, then I stood the pole up in the middle of the tyre, and then I filled the tyre with cement.
The finished product is fine, but I made a bad mess. I don't have a tap out my back garden so I was filling up 5L bottles of water to pour on the asphalt to try brush the cement mix off the asphalt. I've got five empty 5L bottles, and I kept refilling all five of them, so I've poured a few hundred litres of water out on the ground as I brushed it with a sweeping brush. A little bit of the cement also went under the fence and onto my neighbour's back patio (no much though, just a little). Thankfully she's on holidays til Tuesday or Wednesday while I try to figure this out.
I'm hoping my friend gives me a lend of his pressure washer (although I need one that doesn't need a constant water supply).
I'm never mixing cement again, or least not anywhere near valuable property.