Decide your outcome: creamy (stir until thick and spoonable), sliceable (stir to a firmer set), or crispy (set then slice and pan-fry).
Use the ratio from the table and start with slightly less liquid than you think you need; whisk/stir vigorously to prevent lumps.
Simmer and adjust: add small splashes of liquid to reach the same thickness as polenta, then cook until the substitute turns glossy and cohesive.
For sliceable results, spread to a shallow pan and chill until firm before cutting; reheat with a little moisture if needed.
Taste and season at the end: polenta substitutes are neutral, so add salt (and butter/cheese if your dish uses it) to lock in flavor.