Usually the only time you need a slip knot for crochet (unless making a lacey type pattern) is the very first time you attach the yarn to your hook - as soon as you make your first chain out of it for the foundation row it turns into chain number 1. When you make your foundation chain have a look at it as it comes off the hook and it turns into that little v that you count.... this is then a regular chain that you work into on your way back (again, unless making a lacey type pattern). That is the only slip knot you would usually need in a pattern (unless changing colours - some crocheters use a slip knot then too).
Working into the foundation chain can be a little tight so you can always do the foundation chain on a hook a size larger making it slightly easier to work into on the way back.
- the creative cat