Put the apricots into a large saucepan and add 8 cups of water.
Leave to soak overnight.
The next day, put the saucepan on the heat and bring to a boil.
Warm the sugar, and add it to the pan with the almonds and lemon juice.
Stir until the sugar dissolves, then bring to a boil.
Boil fast for about 10-12 minutes, until setting point is reached.
To test, remove the pan from the heat, drop a trickle of jam onto a saucer and leave for a few minutes to cool.
Push the jam on the saucer with the tip of your finger; if it wrinkles, you have a set.
If it doesn't wrinkle, put the pan back on the heat and continue boiling, testing every few minutes until you have a set.
Stir the almonds into the jam, if using.
Pack into warmed jars.
Cover and process in a boiling-water bath, then complete the seals.
Store in a cool place.