Use glass jar and sterilize the jar by filling the jar and the lid with boiling water for 10 minutes.

Wash strawberries, remove the stems, and chop strawberries into smaller chunks. Put it into a large saucepan.

Stir in lemon juice and sugar. Let it sit for at least 20 minutes until the water comes out from the strawberries.

Cook strawberry mixture over medium heat until it boils and the strawberry chunks get soft, stirring often.

Let the mixture cool down in the pot for 15 minutes. Pour jam into the sterilized jar and let it cool completely. Close the lid. Store in the refrigerator.