Using the openlane docker environment, what is considered a successful flow (e.g., ./flow.tcl -design xtea)? Using the xtea design as an example, I see it has negative slack (timing errors), but tritonRoute.drc is empty which I'm assuming means no drc errors. What other possible errors should I look for?

There are 2 drc reports, one produced by TritonRoute during detailed routing and another done by magic during physical verification. The first is found in

reports/routing/tritonroute.drc

the other is found in

logs/magic/magic.drc

. The timing reports under synthesis, should give you a perspective on what clock frequency to use when the design gets out eventually (there is a new feature in the coming release that calculates that for you). Then you have the antenna violations produced under

reports/routing/antenna.rpt

at the end of that document you could see the number of violating pins and nets, you can search for

*

to see what parameters are violated in which nets. Finally, you get the LVS reports, which could be found under

results/lvs/

and

logs/lvs/

which tells you if the final layout have any mismatches with the original netlist (this happens in case of a short, for example). And that's that, I guess.