How to collect slime pass through rice cooker cover when cover on?
I will bump this up to an answer as the only time this should not work for you is if you have a rice cooker that requires a minimum weight to activate the heating element.

You usually should be able to use your rice cooker itself to sear/brown your protein.  Cut into small pieces and toss into the cooker.  Also, garlic, onions, maybe fresh herbs which would benefit from heat to bloom their flavor.  Caramelize any onion or garlic you use and sear/brown meat or poultry just as you would in a pan.  It may take a little longer, and you may not get quite a deep of a browning as you would in a pan, but the same general effect.  It will also help meld the spicing with the protein.

When satisfied, use a little of your liquid to deglaze the bottom of the cooker, you want all that flavor that stuck on.  Then add your rice and the rest of the liquid and cook as normal.  I agree that the bulk of you slime, at least the more unappealing part is probable the protein scum from boiling it, and this should greatly reduce that effect and may give you a more satisfying blend of flavor as well.

My rice cooker is one which with multiple settings which allows it to somewhat double as a slow cooker and I have used this technique many times to make soups with very good results.  If you do have multiple settings, use the highest heat option for the searing of the protein.