I start with 3 field kubbs and throw them. Then, I attack them with my batons. If I knock them all over, I add a fourth field and do it again, adding a field every time I knock them all over. If any remain standing, I gather all the fields (standing or felled) and rethrow them. Penalty kubbs are placed at penalty range, usually towards the far baseline and removed when they are felled (bringing my field kubb total back down). This helps me work on drilling and throwing at fields.
I picked up a cheap kubb set from Menards that has smaller than normal kubbs. The height is the same, but the faces are smaller. I put those on the baseline to work on my accuracy.
Statistically, the opening king toss to decide who throws first is a big indicator of the outcome of the game. Because of that, I try to practice getting as close to the king as possible without making it fall. I'll throw 25-30 batons (one at a time so there is no debris) to work on that.