the.com/soapbox

means A makeshift platform for delivering an impromptu, often loud, personal opinion to anyone within earshot — real or metaphorical.

from Literal soap used to come packed in sturdy wooden crates, and street orators without a proper stage would simply flip one over and stand on it to be seen and heard above a crowd. By the late 1800s 'soapbox' had leapt from the physical crate to the act itself — 'getting on your soapbox' meant holding forth, invited or not, whether you were an actual street preacher or just someone cornering a dinner party with their opinions.