There is no need to peel the pumpkin, just chop into large pieces, scraping away any seeds and soft fibres.
Lay the slices in a large roasting tin and drizzle generously with olive oil. Scatter the garlic cloves, whole and with the skin on, over the tray and season well.
Roast for 35-40 minutes, turning once or twice if you like.
Use a spoon to scrape the soft flesh away from the skin and add this to the stock.