Slots make sense for digital screens. We get it, but they don’t make sense to advertisers. Ask an advertiser what a slot is, and they may not know the answer. Ask an advertiser what an impression is, and they are almost guaranteed to know.
People buy impressions on LinkedIn, Facebook, Google AdWords, Amazon Ads, Pinterest, Twitter, Instagram and Youtube. Stop confusing them. Sell them something they know; sell them plays and impressions, not slots.