The next step after you have mastered the Frog Stand is to refine it so that you are doing it with straight arms. Having your arms straight will mean that your elbows will have considerably less support. This will require significantly more work from your core to hold the position. In addition, this will develop greater shoulder strength and wrist flexibility.
For those working toward the planche, this makes a great intermediary step between the basic Frog Stand and the tucked planche. Many have found that they can hold a Basic Frog Stand for a minute or more, but still be unable to hold a tucked planche for even a second. Proficiency in this straight arm drill will bridge the gap nicely, as it requires a similar forward lean angle to a tucked planche.