Simon Tilts Assembly Guide
Locate the Microcontroller. This component is polarized, which means we need to take extra care to place it in the board properly. Notice the notch:
Now locate the position on the PCB. Again, notice a similar notch symbol in the PCB white ink:
Taking care to align the notch properly, place the ATmega328 into the PCB. While soldering the first leg (it can be any leg you choose), make sure to keep the component flush with the PCB.
When you're done soldering this component, the bottom of your board should look like this - a nice row of even volcanos: