Take the recipe you are using and go ahead and prep it however it says. In the morning make up the batter and if it seems too thin, add more flour and let rise for a little while.

I have had problems with "skinny" sourdough pancakes and I got fed up and just added more flour one day. Tastes good to me and I can make them as thick as I like. Just remember to let rise a little after making the batter--this lets the added flour absorb all the moisture it can and allows the flour's gluten to relax and thus provide a more tender pancake.