Preheat oven to 350°F. Line an 8x8 baking pan with parchment paper, leaving overhang on the sides.

Make the jam. Combine strawberries, guava paste, water, and lime juice in a medium saucepan over medium heat. Cook for 10-15 minutes, stirring and mashing, until the guava paste fully melts and the strawberries break down into a thick, jammy consistency. Stir in the cornstarch slurry and cook another 1-2 minutes until noticeably thickened. Transfer to a bowl and let cool completely.

Prepare the crumble. Brown butter in a small saucepan over medium heat, swirling occasionally, until you see golden-brown flecks and it smells nutty, about 5-7 minutes. Pour into a heatproof bowl and let cool for about 10 minutes.

In a large bowl, whisk together all-purpose flour, almond flour, oats, brown sugar, and salt. Pour the browned butter and almond extract over the dry ingredients and mix with a fork until you get a clumpy, crumbly dough.

Press about two-thirds of the crumble mixture firmly into the bottom of the prepared pan to form a compact, even base layer. Par-bake for 15 minutes until the edges are just starting to turn golden.