There is no public automatcher for this bookie, so you'll need to find your own event following the steps below.
We're basically going to repeat the process of the qualifying bet but using the £30.00 free bet instead.
This time it's worth picking odds greater than 4.0 to maximise your profit, but just bear in mind that the higher they are the more you'll need to have in your Smarkets account to lay it (the "Liability" amount). If you don't have the funds available, just reduce the odds back down.
So go ahead and find another event on both William Hill and Smarkets where the back odds are close to the lay odds.
Once you've found a suitable match, submit the "Back odds" (from William Hill) and the "Lay odds" (from Smarkets) below. They must be decimals (eg. 4.50). The tool will then automatically do the calculations for you and update the next steps.