I've seen advisory boards used in a variety of ways, and all of them work a little different. So ultimately, the question is what is the goal. A few ways I've seen are people that have valuable expertise and experience but don't have the time and capacity to serve on the full board. Also founders that have chosen to move off the board but still want to serve in some capacity. Others, are fundraising representatives or ambassadors from specific communities. Most are volunteer roles, and I've seen some organizations pay a small annual stipend (around $1000) depending on how often they are called upon.