Cut crusts of the bread to form uniform pieces. (Save the crusts to make homemade breadcrumbs in your food processor).
Make 4 stacks of bread, each with 4 pieces of bread in it. Make sure they are cut somewhat uniformly. Then slice each in half so that you have 8 stacks of bread, each with 4 slices of bread in it. These presliced servings will allow guests to easily pull apart a slice.
Make the beet hummus by combining the plain hummus and precooked beets in a food processor. Blend until smooth.
Push the bread slices close together so it resembles a square cake. Remove the top 3 layers of bread, but keep them stacked and in position, so you know where they go. Spread with the beet hummus.
Add the next layer of bread to the top of the beet hummus. Use a spatula or butter knife to spread the flavored hummus on top and then add greens.
Place the next layer of bread on top of the hummus and greens layer. Make sure the bread pieces are tightly pieced together and evenly stacked over the bottom ones.
In a small bowl, use a fork to mash the avocado with lemon and sea salt. Use a spatula to spread the avocado layer onto the bread. Top with the sliced radishes and cucumbers.
Add the last layer of bread to the top of the cake. Top with ½ container flavored hummus. Then add greens, sliced veggies, and seeds if desired.
Serve immediately or store in the refrigerator for a few hours until ready to serve. (You can store it for up to a day, but it will look best when it's fresh.)