Start by combining the raspberry jello with 2 C of boiling water, and stir until dissolved. Remove 1 C of the mixture and set aside in a separate bowl.
Combine remaining mixture with ⅔ C room temperature yogurt and whisk until smooth. Pour into a 9x13" pan and place in fridge to chill until set, about 30 minutes.
Take reserved gelatin and warm slightly if it's become thick. Stir in ⅔ C water and pour over first layer. Place in fridge to chill until set, about 30 minutes.
Repeat this process for the remaining box of jello. Before pouring final layer, place heart-shaped strawberry slices on the 3rd layer in desired pattern. To keep strawberries in place, brush the backside of each slice with a bit of the final layer of gelatin before placing.
Pour final layer of gelatin and place in fridge to chill a final time, at least 3 hours.