when I make vegetarian gravy, I don't use a recipe but essentially
- start with browned/toasted flour (you can make a large batch by roasting in a covered dutch oven at a low oven temp, stirring every 45 minutes or so until it's the rich medium brown colour you want... freeze what you don't need for future use... OR make a small batch by heating over med-low in a dry pan, stirring constantly until the right colour)
- get a vegetable or mushroom stock simmering
- make a roux with browned flour and butter... so, that's not vegan... I'm not sure about coconut oil flavour wise, but some other vegan fat would work
- add simmering stock to the roux, whisking as you add, until it's just a bit thicker than you want the end product
- dissolve a spoonful of marmite (vegemite might do?) in a half-cup of the stock, stir into the gravy (this if for both colour and umami)