You linked to an article that offers no guidance on how to actually do it, which is more indicative of the article itself than of the methodology. One of the vendors in this space has a good amount of content on this topic, which you can find at the bottom of this page: https://www.measured.com/. Dislaimer: I have nothing to do with this vendor or the industry in general (apart from successfully spending money on performance channels).
My apologies I should have prefaced it with "for others confused as to what incrementality is all I could find was ..."
It's a surprise to see a vendor have a clear explanation on their site however - and it's worth quoting i think
>>> Incrementality testing creates an experiment that systematically withholds media channel exposure to a representative subset of users (the control group) while maintaining normal media channel exposure to the broader user set (the test group). If the control group is both sizable enough to be statistically significant and selected at random such that they are broadly representative of the user base, then the media channel’s incremental contribution can be determined by the difference in business outcome (conversion, revenue, profitability, etc.) between the test and control groups.
