It's not exactly slippage (https://www.investopedia.com/terms/s/slippage.asp)

I'm referring to the spread.

Similar to blocktrades exchange. There are no buy or sell orders. You can't put orders on Uniswap as well, just swap token in the moment.

When you go to swap xyz coin, the interface gives you an estimate of how many abc coins you are going to get in exchange. Do that first on the buy side and calculate the price. Then do the opppsite on the sell side (i.e. sell abc for xyz) and calculate the price. I'll venture a guess that the difference is at least 10%, maybe more. That's the spead, and that's the real cost the customer pays (over and above any fees and commission costs that there might be).