All of the ballots in a region contain the same set of candidates. The candidates are organized by riding (the columns) and party (the rows). The voter’s own riding is highlighted and will have its own name at the top; otherwise ballots across the region are identical.
Voters rank as many or as few candidates as they wish, in order, beginning with 1. Ranked candidates may be from anywhere in the region.
Voters who are primarily concerned with their own riding may restrict their preferences to a single column.
Parties, of course, would prefer that voters rank only their candidates. Voters so inclined are more than welcome to do so, of course.
Finally, voters who want to keep it simple are free to vote for a single candidate, just as now.