Sometimes people use a shortened stitch for the first stitch of a round. So if you're using dc, you would ch 2 rather than ch 3, and if you're using hdc, you would just ch 1 rather than ch 2. Obviously, though, this doesn't work too well if you're using sc all the way around.
Here's a tutorial with pictures and explanations, which might help: http://barney.gonzaga.edu/~aburton/crochrnd.html
If that doesn't work, you could try using a smaller hook to create the sl st. Then switch back to your normal size hook. That would be a pain, I know, but it might work!