For doses that don't create a mound above the basket ridge, what is a good method for distribution? I do my best with my finger, but it is sloppy at best.

I am using a 17g La Marzocco ridgeless basket. Dosing anywhere near 17g, puts me way under the ridge, to the point where distribution is near impossible. My normal dose is 18 to 19 grams. A 20 to 21 gram creates enough of a mound in the the basket for a normal distribution (and even some sweep off). I wouldn't have a problem dosing that high, and actually use too. I stop after reading somewhere that I shouldn't be dosing more than 18g on a 17g basket.

If you dose below the rim, leveling techniques like the Stockfleth's Move are of limited use. These threads offer some suggestions:

• Dosing less than level with the rim of the basket
• Proper distribution technique when "down dosing" using WDT
• Downdosing tool
• Stockfleths Move for Dummies
• Down-dosing: how to level when the basket isn't overflowing?

If I'm testing, I weight the coffee in the basket (outside the portafilter) and pay careful attention to dosing evenly as I thwack thwack thwack the doser handle. But when I'm serving a crowd, I use the strikeoff method for speed, with minor corrections with the "Stockfleths Move for Dummies" if required. If I need to downdose, I drag a bowed finger across the basket lip. It's not perfect since the center will have less coffee than the perimeter, but it's fast and workable.

I cover this and more in the Barista Mechanics video:
Consistency Part II covers the more advanced technique I described above:
It's part of the Newbie Introduction to Espresso series.