Good to see you! Glad the rice flour worked for you. I learned the rice flour trick when I lived in Hawaii they use it alot out there.
Start with 1/2 teaspoon flour to 1/2 teaspoon water and make it into a paste then add a bit more of the water to thin it out and mix it into the sauce. This will prevent lumpy sauce. Mix it into the sauce and stir it constantly. If it's no thick enough for your liking add another 1/2 teaspon rice flour and 1/2 teasppon water mix into a paste andd add to the sauce. Once you figure out how thick you like it write it down!
You shouldn't nee more than a teaspoon.
BTW rice flour is great in gravies too you don't hide the wonderful meat flavor in corn starch! (Sorry Mama)