Preheat the oven to 220°C and line two baking trays with baking paper.
Cut the sweet potatoes into evenly sized matchsticks, about 5 mm thick. Place in a bowl or sealable bag, add the arrowroot or tapioca flour and salt and toss or shake to coat evenly. Drizzle over the oil and toss or shake again.
Arrange the sweet potato matchsticks in a single layer over the prepared trays, leaving space between them. Bake for 15 minutes, then flip with a spatula and cook for a further 10–15 minutes, or until the fries are crispy and starting to turn golden brown in spots.
Meanwhile, to make the chunky diced lime and chilli Shepard avocado, gently toss all the ingredients in a bowl until well combined keeping the avocado nice and chunky.
Pile the sweet potato fries onto a large platter and top with generous servings of the lime and chilli Shepard avocado, sprinkle over the coriander leaves, season well with salt and serve with the lime cheeks for squeezing, if you like.