Ok , at first , looking , it appears it supply voltage is simple DC . but it is not correct . because the frequency of current will be about 18.432MHZ . thus you should connect a capacitor from DC supply to the VCC pin of IC , nearby of that .
Ok lets come back to the polygon issue : at high frequencies it is better to use continuous polygon . but your frequency is not very high . so you can use a simple polygon , with windows ( at high frequencies , it should not has windows ) . and you'll need to connect your ground to the polygon .( the microcontrollers are sensible to noise ) thus you can protect your circuit from the area noise . if your area has many noise that produced by machines ( the places , for instance , factories ) , you can use two layer board , that it's second layer is just polygon , that connected to the ground , to be ensure that noises can't destroy the behaviour of your circuit.
Good luck
Goldsmith