curb for a monolithic slab
We typically set & pour the curbs at the same time. We use long steel stakes to control the height and 1x2's as spreaders to control the width. We pull the spreaders first, so that we can do a good job of leveling the top of the curb & so we can edge it. We wait a little longer to pull the stakes, and then fill them with a little concrete each. An inside radius/curb tool will make the finish job a little easier, but to be honest, this can be a fairly complex & laborious job for most DIYer's to attempt, especially if the concrete's setting relatively fast.
On large slabs where the slab itself is level, we've laid solid 4" or 6" half course block in the past as well. You need to install longer anchor bolts in the slab though, and a little lay-out to keep them near the ends of the block is ideal. You'll want to check how much bolt embedment you're required to have by code (here it's 7" minimum) and add in for the height of block (4" in what I referred to) and also enough for the sill plate (typically 2-2.5" here, for a total of at least 14" bolts)............