Messy vs. Sloppy
There's a big difference between messy work and sloppy work. Tricky thing is, to an outside observer, they don't look that different.
Quality work, even when conducted carefully, is often messy, especially in the early stages. The exploratory phase requires moving stuff around. Trial-and-error. Errors are messy. You have to be okay with a mess, within reason, to figure out what works best. Some things have to be left to chance--but intentionally, not arbitrarily. Mid-process, it might seem like everything is in chaos, even when it isn't.
Sloppy work is careless. Sloppy work generates true chaos, because it leaves stuff to chance arbitrarily rather than with intentionality. Sloppy work happens when someone doesn't care enough to be intentional about the mess. It spills over a reasonable boundary. It's a truly chaotic mess that's been left to its own devices.
Another distinction: those in a messy but careful process know about the mess they're making. They can find things in the mess, because they know what made the mess. They have a mental map of it. If you ask someone in a sloppy process, they won't be able to tell you where things are--at least not consistently.
Yet another distinction is that the mess involved in quality work doesn't last that long. It gets cleaned up when the process is complete, or at least when the process reaches a certain iteration. Sloppy processes remain so, because, well, sloppiness is self-perpetuating.
Don't be afraid of competent people making a mess while they're doing quality work. You can tell them from the sloppy ones. If they're driven, encouraged, and energized amidst the mess, it's not sloppy. If they're despondent, distracted, or unmotivated, there's a good chance the mess they're making is a sloppy one.
And if you can't tell right away, just wait. It'll become clear soon enough.