The scatters are the letters G, O, L, and D. You’ll be given 12 free spins if you manage to land 4 of them to start the Free Spins feature. Additional scatters on the trigger spin will give you 5 free spins.
For instance, getting six scatters to start the free spins would award you 22 free spins. There are more possible spins because the Reaction function is active during the feature.