Don't forget the cardboard concrete "tubes" [forms]. If you plan it all out you can do the entire project in one pour. You'll have to build a form for the top that is temporarily supported and strong enough to hold the weight while it all cures. Three or more cardboard tubes that are placed in the ground with the bottom below the frost line and rebar placed in them will form the legs. You can pour footers or use packed stone at the bottom of the holes. The rebar should extend into the top but not beyond the upper surface of the top. The form for the top must have holes corresponding to legs and supported to hold the weight. You pour concrete for the legs and begin pouring the top. Add some wire screen as you continue to pour the top and then finish the top smooth. You end up with one monolithic concrete table.

It takes some pre-planning and a fair amount of form work but you end up with three or more round legs, a top bonded to those legs and no block work. If you can get the concrete delivered to your site, it's a few minutes to pour the concrete, vibrate to settle, finish the top and you're done.
If you didn't want to make the top and legs as one unit you could pour the legs and leave a threaded anchor protruding from each leg. The top is then poured as a separate unit with corresponding, holes formed with a step (countersink) to match the anchors. PVC reducers make nice forms for those counter sunk holes. The top is placed over the anchors, washers and nuts are used to secure the top and a little concrete is poured into the holes to plug them and make the top flat.