I have cured my own olives a few times. I do not slit them. I simply wash them and clean them of stems, and pack them in sterilized jars with a hot brine that is only salt and water, no vinegar. It seemed like it took 2 or 3 months for them to be ready the first times, but last time, it took over 6 months. I open a jar, and rinse, taste. If it does not taste like an olive, rebrine, and back to the cellar. They change from very hard to medium-soft. This is the technique that I was taught by older Italians. I bought "Feast of the Olive" to learn other techniques, but have found none better. This is off the top of my head; I hope I am accurate.