Prep the cucumber: Wash and dry it well. If using an English cucumber, you can keep the peel on for color and texture. Slice it thinly—about 1/8 inch or thinner. If using a standard cucumber, peel it and scoop out the seeds first for less water.

Draw out moisture: Lay the slices on a paper towel or clean kitchen towel. Sprinkle lightly with salt and let sit 10 minutes. Blot gently. This prevents soggy sandwiches.

Make the spread: In a small bowl, mix cream cheese, butter, mayonnaise (if using), dill, lemon juice, and lemon zest. Add a pinch of salt and a few grinds of pepper. Stir until smooth and spreadable.

Toast, if you like: For a sturdier sandwich, lightly toast the bread so it’s just set but still soft. Let it cool before spreading, so the spread doesn’t melt.

Spread both sides: Evenly spread the mixture on one side of each slice of bread. Coating both slices seals in moisture and keeps the bread from getting soggy.

Layer the cucumbers: Arrange cucumber slices in neat, slightly overlapping rows on half the bread slices. Don’t pile too high; 2–3 layers is plenty for crunch without slipping.

Season smartly: Add a tiny pinch of salt and pepper over the cucumbers. A sprinkle of flaky sea salt is especially nice.

Close and press: Top with the remaining bread, spread-side down. Press gently to help everything hold together.

Trim and cut: For a classic look, trim the crusts using a sharp knife. Cut each sandwich into rectangles or triangles. Wipe the knife between cuts for clean edges.

Serve now or chill: Eat right away for maximum crunch, or chill for 15–20 minutes to firm them up before serving on a platter.