Replacing Formica on countertop

[fixtureman]

Few recommendations. Do not glue over laminate. Just cause. A heat gun can help remove old laminate. If that doesn't work, lacquer thinner poured from a bottle of choice (mustard bottle, solvent specific bottle) in between laminate and substrate. If this is the way you proceed, allow substrate to dry. Preferably overnight. I usually use a rag and more thinner to clean as much glue from the substrate as possible. It just makes things easier.

If you decide to make new, whichever material you can get will work. I've worked in shops that prefer only particle board. Others only use plywood, preferably birch. My former shop foreman swore by MDF, all work well, all hold up.

Just be sure that there are no open flames and take the rags out side.

[Cooler]

Particleboard is cheap and easy to cut.  It seems to be the substrate of choice for Formica.  I would replace it.  If it is over a dishwasher or just near one, then coat the underside or the steam will cause the particle board to disintegrate.