Golden rocks obtained by training Slayer are part of the Statue of Rhiannon. Two are required each to complete the statue each time that it is built. Golden rocks may be stored inside a statue collection bag.
Killing monsters on a slayer task. The highest slayer master available is recommended so more monsters are given per assignment. Slayer contracts from Markus will yield slayer rocks without needing a task. Recommended repeating crawling hands contract and can double up slayer rocks and melee rocks. When using a bonecrusher you could triple efficiency by including prayer rocks.