Peel potatoes, sweet potato, and carrots. Cut the potatoes in half and slice up the sweet potato, carrots, and pumpkin into desired sizes. (note 4)
Half fill a large pot with water and stir in salt and baking soda (bicarb). In the water, place the potatoes and sweet potato. Bring to the boil and simmer for around 10 minutes until the potatoes feel soft. Then strain in a colander and allow to cool.
In a large mixing bowl place sliced pumpkin and carrot and drizzle olive oil over the vegetables. Add 1/2 tbsp of garlic salt, rosemary, and thyme to the bowl and gently toss until the pumpkin and carrot have mixed well with the herbs. Season with black pepper if desired.
When the potatoes have cooled, separate the sweet potato from the colander, these will not need roughing up. Toss the potatoes around in the colander until they form rough edges.
Place the potatoes onto a large plate with the sweet potato and drizzle with olive oil. Season the potatoes with a 1/2 tbsp of garlic salt, rosemary, and thyme.