Blake is pretty exposed, I would not recomend anchoring there unless you are pretty confident in your skills. You can anchor
with one hook on the west side, but the wind and currents need attention, it is also deep in spots. The rest of the island is even more open and you will rock all night with ferry and shipping traffic wakes. Blakely Harbor about 20 min north is a better choice. Another fun option would be the Bell Harbor marina in downtown Seattle, you might be able to get a reservation there, the marina at Blake is first come first served.