Before I even think about attacking I wall off the North, East, and West entrances to the base with Bramble fences and 12 SB towers each. This is in addition to the 2 AA towers at the North and East built in the first part to assassinate the scouts.
This strategy requires a LOT of coal, so only go to level 3 and build some chameleon/polar bears (cham head and tail). About 8-12 will give you enough guards to colonize the coal between you and the dark blue base with the henchmen from the initial pile. Level up from there and colonize in the center. Any coal you take in the middle, EXEPT for the one on the ledge just North of your base will be unmolested as long as the henchmen dont get spotted.
Chamopotomi and Rhinobsters are what I use to take out the three bases. I also increase the number of SB towers at the north and east entrances to the main base to 16-20 and the AA towers to 4-6. With upgraded towers and fences, and some help from Rex's gun, you can repel any invasion while you build up your attacking force in the water south of your base.
DON'T labrush Velika, crush her entire base. I learned that one the hard way.