Contribute personal land
Transfer ownership
Stand on your personal claim and use /claim guild contribute. Read the prompt, then /claim guild contribute confirm.
The guild owns the land afterwards. It uses guild budget and frees your personal budget.
You need the Claims right and enough guild budget. With multiple guilds, include the tag in confirmation too, e.g. /claim guild BAU contribute confirm.
You keep manage, trusted players keep their levels until guild management changes them. Purchased land cannot be contributed.
Leaving and possible returns: /help guild-return.