Here's an imaginative 4-minute film from 1905 by James Williamson about a man who gets so wrapped up in the book he's reading that he is oblivious to the world around him. (Yes, had I known about it a month ago I would have included it in this post about the "oblivious gag.") YouTuber changebeforegoing labels this "the first slapstick movie." I would argue the point, but of course it all depends on how you define slapstick.
That was the earliest example I've seen of the steamroller-flattening routine, which reappears in 1909 in Slippery Jim, though without an actual steamroller. It later became a trademark gag of Ringling clown Paul Jung, and was reprised with a twist by Mel Brooks in Silent Movie. See this post for those examples.