Filling deep gaps in sub-floor between plywood and concrete

The pier and beam foundation under the corner of the bathroom was rotten and collapsed. At some point concrete was poured over the entire bathroom. Hammered through the concrete and installed new pier, joist, and plywood sub-floor. There are some pretty major (and deep) gaps where the plywood meets the concrete. How should I approach filling these gaps with the goal of applying self-leveling underlayment and flooring (probably tile).

Thanks for any advice!

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