Drain the salmon and add it to a bowl. Add ¼ cup almond flour, the egg, 1 tbsp lemon juice, 1 tsp lemon zest, salt, and garlic powder. Mix until combined.
Cut a slice of cucumber and place it next to the cutting board as a reference. Divide the salmon mixture into 20 pieces. Shape them into a disc the size of the cucumber slice and place them on the cutting board.
Add the remaining almond flour to a bowl and coat the salmon disks. Coat them carefully without distorting their shape and size. Place them on a plate and transfer them to the freezer for 10 minutes.
To a small pan over medium heat, add the oil. Add croquettes to the pan and cook for 3-4 minutes per side until golden. Drain on paper towels.
To prepare the aioli, add the mayonnaise to a bowl. Add ½ tbsp lemon juice and 1 tsp lemon zest. Whisk to combine, then transfer to a piping bag.
Slice the cucumber into 20 discs and divide the lettuce leaves into pieces slightly larger than the cucumber slices. Lay all the cucumber slices on a flat surface and pipe a little bit of aioli. Add a piece of lettuce and pipe once more.
Add the croquettes on top of the cucumber and lettuce. Pipe more aioli on top. Finish off with a sprig of dill, and serve.