You have to have a food processor for this. A blender might work? But I'm not sure. A food processor really is the best way. I've made this twice now and adjusted it slightly the second time--it was just perfect.
1/2 cup green olives
1/2 cup pitted kalamata olives
1/2 cup walnuts
1 clove garlic, mashed
1 Tablespoon ground flax seed
Freshly ground pepper
Put the olives in a colander and give them a quick rinse. This will cut back on a little bit of the saltiness--it will still be plenty salty though, don't worry! Add all of the ingredients except the olive oil to a food processor and pulse until combined. Drizzle in the olive oil while the machine is running, scraping it down once or twice, until desired consistency is reached. This is meant to be a dip, so don't make it too runny! Serve with crackers or thinly sliced bread.
You could substitute pine nuts for the walnuts, or use a different kind of oil (grapeseed oil might be nice). You could skip the garlic or add more of it, and you could experiment with different kinds of olives. I imagine stirring in crumbled feta at the very end would be delicious too. You should have fun with this and experiment away!