Place the dill umbels and horseradish leaves at the bottom of a clean, sterilized jar, pack the cucumbers in (not too tight), then top with garlic cloves and bay leaves.
Pour in boiling water, cover with a lid and leave for 40-60 minutes until cooled.
Drain the water and pour in fresh boiling water again; let the cucumbers steam for about another hour.
Drain this water into a saucepan and bring to a boil. Add salt and sugar to the jar and pour in the vinegar.
Pour in the boiling brine and seal the jar.
Wrap until morning, then unwrap and store in a dark, cool place.