Potting new lithops

Hello! First time lithops keeper

I’ve acquired some nice pumice, lava rock, and pon gravel to mix with a small percent of sandy succulent soil.

I’m wondering if I should plant the older leaves beneath the substrate?

I know the new leaves consume the old ones, so I won’t remove them. But do they need to be above the substrate?

Pictured are two lithops with old leaves receding. Plant above gravel or below?

Also I’ve seen online – you should keep them separate because they may be at different growth stages, requiring different types of care. Is this important, or can I plant together?

by mailmangirl