To toast your nuts, lay them out in a single layer on an unlined baking sheet. Toast for 10 minutes in a preheated 350F oven.
Put the nuts, sugar, and salt in a high speed blender or food processor. Blend until the nut butter is smooth and creamy. In my Vitamix this took just a minute or two, and I did use the tamper to push the nut mixture down toward the blade to get everything evenly processed. When the nut butter is done it will flow freely in the blender.
Take a taste of your walnut butter at this point, and add more sugar or salt if you like. If you do adjust any ingredients, blend again briefly to combine.
Transfer the butter to a jar. It will be warm and quite soft at this point (and utterly delicious so be sure to steal a spoonful for yourself.) Refrigerate it and it will firm up. I like to store it in the fridge, this keeps it fresh and prevents the oil from separating out.