Preheat the oven to 350°F and line an 8x8-inch baking pan with parchment paper, leaving overhang on two sides.
Mix the almond flour, erythritol, salt and melted butter until it looks like wet sand. Press firmly into the pan and bake for 10 minutes.
Simmer the raspberries, 3 tbsp erythritol and lemon juice in a small saucepan for 8 to 10 minutes, mashing the berries, until thick and jammy. Off the heat, stir in the chia seeds and let cool for 10 minutes.
For the frangipane, beat the softened butter and erythritol until creamy. Beat in the eggs one at a time, then the almond and vanilla extracts. Mix in the almond flour, baking powder and salt until smooth.
Spread the jam over the crust, leaving a small border around the edges. Dollop the frangipane on top and gently spread it to cover the jam, then scatter the sliced almonds over the surface.
Bake for 25 to 30 minutes, until golden and set in the center. Cool completely in the pan.
Whisk the glaze ingredients until smooth and drizzle over the bars. Let set for 15 minutes, then lift out and slice into 16 bars.