Arrange the rusks on a serving platter or individual plates.
Drizzle 3 tablespoons of olive oil evenly over the rough upper surface of each rusk. Let rest 2-3 minutes while you prepare the tomatoes.
Halve each tomato across its equator. Hold one half cut-side down against the large holes of a box grater over a wide bowl. Grate firmly in circular strokes until only the skin remains in your hand. Discard the skins.
Spoon the tomato pulp generously over the oiled rusks, allowing it to run to the edges.
Crumble the feta or mizithra generously over the tomato layer.
Rub dried oregano lightly between your palms and scatter over each dakos. Add a pinch of flaky salt.
Finish with the remaining 3 tablespoons of olive oil, poured in a slow thread across each piece.
Serve immediately - dakos does not improve with time.