Identify your use: baking/cooking (neutral oil) or finishing/flavor (nuttier oils or flax gel).
Match the ratio: use 1:1 for neutral oils; use walnut oil at about ¾ the amount if you want the flax-like taste.
If your substitute is wetter (flax gel), reduce added liquid slightly and expect a thicker batter.
For any omega-3 goals, treat flax gel as a partial surrogate—its nutrition won’t perfectly equal bottled linseed oil.
Taste and adjust after cooking: if flavor is missing, add a small drizzle of the substitute to the finished dish.