In the UK and Australia, people "lay" the other outcome on a betting exchange (like Betfair). The US barely has liquid exchanges, so we use a different method: dutching.
Dutching
Instead of laying on an exchange, you back the opposite outcome at a different sportsbook. In a two-way market (e.g. baseball moneyline — one team must win), you put the bonus on Team A at one book and cover Team B at another.
Bonus Edge's tools are dutching-first for exactly this reason. The Converter finds the best opposite-side price across every US book and tells you precisely how much to stake to lock in the same result either way.
When an exchange exists
A few states have exchange-style books (Sporttrade, Prophet X). When one is available, the Converter will also offer a "lay" option. But dutching is the bread-and-butter US method.