Can I put my merino base layer in the dryer?

Technically yes, on the lowest heat setting only, but air drying flat is strongly recommended. Even low dryer heat can cause gradual shrinkage over multiple cycles, and any mistake with heat settings can cause irreversible damage. The safest approach is to lay the garment flat on a clean towel, roll it up to remove excess water, then lay it flat to dry. If you must use a dryer, use the air-fluff (no heat) setting and check frequently. Never use medium or high heat.