Combine chopped strawberries, figs, and sugar. If you're not going to make the jam right away, funnel them into a sealable container and refrigerate for up to 48 hours.
When you're ready to make the jam, prepare a small boiling water bath canner and three half pint jars. Place lids in a small saucepan and bring to a bare simmer.
Scrape macerated fruit, juices and any undissolved sugar out into a 12-inch skillet. Place over high heat and cook, stirring very regularly, for 8-12 minutes. Add lemon juice towards end of cooking.
Jam is finished when the volume has reduced by 1/3 to 1/2. Another way to test for doneness is to drag your spoon or spatula through the jam. If the space you've created doesn't fill in immediately with jam, it is done. Before canning, taste and add more lemon juice, if necessary for brightening.
Funnel jam into prepared jars, wipe rims, apply lids and rings, and process in a boiling water bath for ten minutes.
When time is up, remove jars from canner and place them on a folded kitchen towel to cool.
When jars are cool enough to handle, remove rings and test seals by gripping the edges of the lid and raising the jar up about an inch holding only onto the lid. A well-sealed jar should hold fast.
Sealed jars are ready for pantry storage, where they'll keep for up to one year if left unopened. Any unsealed jars should be refrigerated and used promptly.