In Ellingham diagram, the slope of the curve of the formation metal oxide

Among the methods for extracting metals from their ores, i.e., 1. roasting a metal sulphide, 2. chemical reduction of a metal oxide, and 3. electrolysis, the preferred method depends on $E^{\circ }$ value for the reducing half-reaction:

$M^{n+}(aq)+n{e}^{-}\to M(s)$

Which method is preferred for the metals with the most negative $E^{\circ }$ values?