Prepare the raspberry sauce first. Combine the raspberries and sugar in a small saucepan and crush using a large fork or potato masher. Cook the raspberry sauce over medium heat and bring to a simmer. Simmer for 3 to 4 minutes, then pour over a fine-mesh sieve. Using a spatula, press the syrup through the sieve, discarding the remaining seeds.

In a separate pot, sprinkle 1 tbsp agar gelatin over 2 cups cold water. Allow the mixture to stand for 5 minutes, then cook over medium heat for 4 to 5 minutes. Bring the mixture up to a low simmer, then add the raspberry sauce. Mix and cook for 1 minute. Remove from heat and add 2 cups ice water. Stir until the ice is completely melted.

For the jello to set at a diagonal, set the cups at an angle over a muffin tin. Fill the cups half way and carefully transfer the cups into the refrigerator to set completely. Agar sets fairly quickly. The first layer will set in about 30 minutes.

For the next layer, repeat the same process. Sprinkle 1 tbsp agar gelatin over 2 cups cold water. Allow the mixture to stand for 5 minutes, then cook over medium heat for 4 to 5 minutes. Bring the mixture up to a low simmer, then add the concentrated juice. Mix and cook for 1 minute. Remove from heat and add 2 cups ice water. Stir until the ice is completely melted.

Pour the jello mixture over the first layer. Add berries and fruit to the jello mixture before it sets. Transfer the cups back into the refrigerator to set completely.