This article explains the length of the process.
By law, it can last a maximum of 24 months, unless the authority needs to consult different authorities on your case. During this period, all applicants must have at least temporary residence in Slovakia, which usually means they have to spend at least 183 days per year in the country.
Once registered, Slovak authorities do not track the actual days of stay, as European borders are open. Individuals with pre-existing residence in another EU state have a more advantageous regime. Again, exceptions might apply.
SLAC holders have very simple access to residence permits with a few requirements.
Generally, the most important step of the process is to arrange a Slovak address where you will stay during your residence permit.