Plywood to the interior size of the sink base.
How to fix floor under kitchen sink.
In from all four edges.
Measure the size of the area under the sink.
Cut a sheet of plywood to fit this area.
Next cut a piece of 1 2 in.
Then cut out the middle section of the swollen sink base with a jigsaw.
Always use a blade guide for safety when cutting with this type of saw.
Remove all contents from the sink.
Use a circular saw to make your cuts.
Then trace a cutting line about 3 in.
Cut a new piece of plywood to fit.
Remove the old swollen floor.