Lightly oil the slow cooker insert.
In a large bowl, combine the oats, rice, almonds and salt.
In a medium bowl, combine the maple syrup, olive oil, brown sugar, almond and vanilla extracts. Whisk to blend, then pour over the oat mixture. Stir to mix well.
Scrape into a large slow cooker and turn it on high. Place a wooden spoon or chopstick under one side of the lid, to hold the lid ajar.
Cook for 30 minutes, stir, cook for 30 minutes, stir, and cook for 30 minutes more. Spread on a sheet pan to cool, then gently mix in the raisins.
Cool on a rack. When completely cool, break into large chunks and store in jars or tubs. Keep tightly covered at room temperature for up to a month, or freeze for 4 months.