I'm having trouble with the smoothness of where my flooding and outlining icing meet. I try to use the "toothpaste consistency", 20-second RI (royal icing) when outlining, then a thinner consistency when flooding, but a lot of times it looks like this picture. Other times it's very smooth. I don't get it! Any advice? I usually outline all of the cookies, then move onto flooding.
When I make a lot of cookies of the same design, I outline all of them first then flood them. When flooding I flood to the very edge of (almost over) the outlines, so that the outlines won't show so much. I think it's important to put enough icing for flooding to get the flat smooth surface.
I agree with all that's already been said. I would add that it looks like your flooding icing was a little too loose (and also thinly applied), so it settled and sunk more in the middle than it has to. Try working with a slightly thicker consistency and doing what the other two ladies (above) said if you don't want to see the outline along the edge.
If I want a line, I use thicker icing, and a larger nozzle and just take care to make the line really neat.
If I don't want a line, and I'm doing a lot of cookies, I will use a 10 second consistency for the line and a quite small nozzle (eg PME 1.5), and immediately flood with approx 5 second flood, so it will all settle by itself.
If I'm not doing a lot of cookies, and can't be bothered to make seperate icing bags, then I'll only mix the 10 second consistency, and outline and flood immediately, then I usually shake the cookie to settle the icing. If it's a delicate cookie, I hold it gently in my left hand, and 'vibrate' my left hand with my right, if that makes sense? Evens out a whole lot of problems with the flood!