Ok to conceal electrical junction box under cabinet behind removable toe-kick
The definition of readily accessible in the National Electrical Code.


  Accessible, Readily (Readily Accessible). Capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is requisite to actions such as to use tools, to climb over or remove obstacles, or to resort to portable ladders, and so forth


Junction boxes above drop ceilings are considered Accessible but if you have to remove part of the building (such as a piece of drywall) then it is NOT  accessible. I had a house where the panel was behind some paneling that was hinged. This is usually acceptable to the Inspector.

Bottom line is if you can easily access it, and if you leave information as to where to find it, it should fit the definition if Accessible.