The present invention is directed to a method of making a transformer having a stacked core, which includes top and bottom yokes and first and second outer legs. The core also includes an inner leg that is formed from a pair of stacked plates, which abut each along a seam that extends in the longitudinal direction of the inner leg. Each of the upper and lower yokes may be formed from a single stack of plates, or a plurality of stacks of plates. Each of the inner and outer legs may also be formed from a single stack of plates, or a plurality of stacks of plates. The cross-section of the core may be rectangular or cruciform.