Preheat the convection oven to 300°F (150°C) and line a heavy-duty rimmed baking sheet with professional-grade parchment paper or a silicone baking mat.

In a large stainless steel mixing bowl, combine the rolled oats, sliced almonds, pumpkin seeds, cinnamon, and sea salt. Stir until the dry particulate matter is evenly distributed.

In a separate glass bowl, whisk the egg whites vigorously for approximately 60 seconds until they become frothy and lose their viscosity.

Slowly incorporate the maple syrup and vanilla extract into the egg whites, whisking until the mixture is homogenous.

Pour the liquid mixture over the dry ingredients. Use a rubber spatula to fold the mixture repeatedly until every oat flake is thoroughly hydrated and coated with the egg white solution.

Transfer the mixture to the prepared baking sheet. Spread into a uniform layer and press down firmly with the spatula to create a compressed slab; this step is critical for cluster formation.

Bake for 45 minutes. Rotate the baking sheet 180 degrees at the 22-minute mark to ensure even heat distribution. Do not stir the mixture at any point during the baking cycle.

Remove from the oven. The granola will still feel slightly soft but will harden as it cools. Allow to reach room temperature undisturbed on the baking sheet for a minimum of 60 minutes.

Once fully set, manually break the slab into desired cluster sizes. Store in an airtight container to prevent atmospheric moisture absorption.