In EDM music the kick is one of the main elements. When it comes to Big Room and Festival tracks I like to layer a sine sub bass with the kick to create this dancing tension. It is like the kick is creating the rhythm and the sine (which is more felt than heard) is driving you with its sub sonic power to the next hit.
Most of the times I design it while I produce the song and not before, so knowing the melodies and the characteristics of the instruments I use e.g. in the Drop section, gives me the whole picture on which I want to construct it. It is critical to know how and when to sidechain the sub bass both for attack and release to glue with the kick and most important with rest track.
Sub bass needs very special treatment as it can easily distort when compressed and ruin the result. I find it easier to adjust its settings using headphones rather than drive my monitors too much. Most of the times I use Operator synth from Ableton live, keeping just one osc and use sine wave. I like to choose the fixed mode and tuning my sine to the proper sub frequency of the tonic note of the track. If e.g. the track is on G minor I tune to 49 Hz.
One of the most common issues is the introducing of a disturbing click sound in the beginning. There are some things we can do to treat it like adjusting volume's ADSR envelope to smoothen it and/or disabling the re-trigger option of our synth. In this step I try to eliminate 100% this click so I will know that I will not have to deal with it afterwards.
When finishing that, it is time to put my kick back and playback along with the sub. Here is where I define the final volume level of the sub on time axis. Using compressor or some envelope shaper plugins (like shaper box from cableguys) helps me to make the sub bass glue with the kick and enhance its power. It needs some attention because the sub can be easily distort in this step so some solo checking is needed. Finally putting it playback with all tracks and make the final adjustments. And do not forget to check it in solo once again, we do not need it to distort!