Dimples can occur when the resin cures in cooler temperatures, or if there is a temperature dip in the first 24 hours of a cure. Always aim for a stable room temperature of between 72-77F or 23-25C when curing your artwork.
Dimples can also result from surface contaminants ( such as dust particles ) landing in your wet resin. Ensure your resin room is as free of dust as possible and always use a dustcover to protect your work while it cures.
Dimples can also result from overtorching. Make sure you only lightly pass the torch two or three times over the resined surface, always keeping it moving, and don't hold it too closely or in one place for too long.