The main reason for partisan gerrymandering in the US is that in most states, redistricting is handled by self-interested politicians in state legislatures. The most commonly proposed reform would take gerrymandering out of politicians’ hands entirely, and let an independent nonpartisan commission handle the job.
Several countries have found this works well. Canada, for instance, used to have a serious gerrymandering problem, but it shifted to independent commissions in the 1960s. Each province has a three-person commission whose members are usually judges, social scientists, or retired public officials. ”Today, most Canadian ridings [districts] are simple and uncontroversial, chunky and geometric, and usually conform to the vague borders of some existing geographic/civic region knowable to the average citizen who lives there,” JJ McCullough has written.
Commissions elsewhere can be more controversial. Some US states have ostensible redistricting commissions, but let politicians name the appointees. Some countries have avowedly nonpartisan commissions that end up doing the parties’ bidding anyway. The specific instructions of these commissions also matter, since some are charged with creating competitive districts that could go either way, while others are charged with ensuring representation of different groups or interests.