The first step in ensuring an even burn with pillars is to allow candle tunneling. Tunneling occurs when a candle burns down the middle, leaving the outer wax untouched. Helping create an ambient glow from within. 
It’s important to trim the wick to about 1/4 inch before lighting the candle. This will allow the wax to melt evenly around the wick, allowing the formation of a hollow space. Additionally, when lighting a new candle, it is important to let it burn for at least an hour or until the wax has melted almost all the way to the edges of the candle. This will create a "memory burn," which will help the candle to continue to burn evenly in the future. As pictured