Preheat oven to 375 degrees.
Place bread slices on baking sheet. Brush both sides with olive oil and sprinkle each top with a pinch of salt. Bake 7-8 minutes, turning the sheet halfway through cooking to ensure even browning. OR, place bread slices in a hot grill pan for a few minutes until nicely browned. Remove from oven and allow to cool before serving.
In a skillet over low heat, toast walnuts 5-7 minutes then remove from heat, cool and chop finely; set aside.
In a small bowl, mix ricotta, lemon zest and parsley; cover and refrigerate until ready to serve.
Over medium heat in a skillet, add olive oil, 2 tablespoons butter and red pepper flakes. Add apples, squash, rosemary, sage leaves, salt, pepper and stir to combine. Reduce heat to low and cook 15-20 minutes until squash and apples are fork tender (if the mixture becomes too dry, simply add a few tablespoons of apple cider or water and allow it to cook down).
Turn off heat and remove sage leaves. Add 1 tablespoon honey and remaining 1 tablespoon butter. Taste for seasoning and cool to room temperature.
To serve, spoon a teaspoon of ricotta mixture onto each crostini, top with a teaspoon of apple/squash mixture, sprinkle with walnuts, drizzle with honey and a pinch of salt. Serve immediately.