How to buy a dot with ETH?

Could you please elaborate on the process of purchasing DOT using ETH? I'm particularly interested in understanding the steps involved, any prerequisites I may need to fulfill, and any potential risks or considerations I should be aware of. Additionally, could you provide some insights on the best platforms or exchanges to facilitate this transaction? I'm also curious about any fees or commissions associated with the purchase, as well as the estimated time it would take to complete the transaction. Thank you for your assistance in clarifying this process.