Earlier carrier losses leave construction lead times

If Japan lost its carriers in April instead of June, could a replacement class be laid down earlier?

Only to a limited extent, because ordering and substantial preparatory work already precede laying down the ships.

Moving the carrier losses from June to April would leave much of the preparatory work unchanged. Orders and other work have to precede laying down the replacement ships. Some acceleration is possible, but the answer expects only a limited change in the construction start.