My wife started from a standard Japanese recipe, and has modified it to our tastes.
But here is a good simple recipe in English:
https://norecipes.com/ikura-salmon-caviar/
The key is to start with fresh salmon roe, and to keep everything clean and cold.
Separating individual eggs from the skein is the hardest part. Some recipes call for manual separation, others quickly blanch the skein in hot water to remove the retaining membrane. My wife uses the hot water technique.
We also refrain from adding sugar, and use mirin instead of sake. The mirin has enough sweetness for our tastes. Also, choose a good quality Japanese soy sauce ("shoyu", we use Kikkoman or Yamasa). Chinese or Philipino soy sauce works well for Chinese or Philipino dishes, but not ikura.
The cured ikura will last a couple weeks in the fridge, depending on how salty you make the brine. You can also freeze it in small containers.
Careful not to mistake your cured bait for ikura!