To ensure that my commissions / YCHs can be completed and delivered to my clients at a satisfactory pace I can only take so many at a time. Open slots mean I have time to take on another project for a client. If all the slots are closed then I am too occupied with current work to take on more.
Give me a week or two and check again to see if more slots have opened up!

Commission Slot #1

COMMISSION SLOT #2