Implement Early Stopping After Certain Number of Epochs

How can I implement keras’ EarlyStopping() callback function after only a certain number of epochs has passed?

My model has a lot of fluctuations in the accuracy and loss in the first few epochs, so implementing early stopping from the start would cause my model to stop training much too early. How can I implement early stopping after a certain epoch (say, 20) when my model has stabilized?