If you want the particle board to be washable and durable, then apply two layers of sealer over the stain. Polyurethane or acrylic varnish will be suitable for indoor use, but if your board is going be outside, you will want to use acrylic or an oil-based varnish.
What is the best way to protect particle board?
Sealing with a good quality sanding sealer or even plain lacquer will strengthen particleboard. They prevent moisture penetration on all sides, including the edges. In time, the particles will separate as the glue loses adhesion.
Can you seal a particle board floor?
Apply sealant with a paint brush to all sheets of the particle board on the floor, making sure to have even coverage of the face on each sheet. Work from one end of the room to the other moving backward as you apply sealant. Let the sealer dry thoroughly.