In a large mixing bowl, toss cucumbers with salt to coat, then cover with ice cubes and refrigerate. After 1 to 2 hours, drain, rinse thoroughly and strain to remove excess water. Set aside.
In a saute pan, heat the olive oil over medium heat. Add the asparagus, carrots, peppers, onions and garlic and saute for 3 minutes or until the vegetables are just beginning to soften. Transfer to a large bowl. Add the cucumbers, oregano, thyme and peppercorns and gently toss to combine.
Return the saute pan to medium heat and add the vinegars, sugar, fennel seeds and bay leaves. Simmer until the sugar has dissolved, stirring constantly, about 3 minutes. Pour the syrup over the vegetable mixture and toss to coat.
Cool to room temperature, then cover and refrigerate. These are best eaten a few days after they have been made, but can be eaten after chilling for a few hours.