Is there any resources on how one should go about doing this “make your own index fund” manually? I live in the EU, and of course, I cannot just use this tool.

Is there any resources on how one should go about doing this “make your own index fund” manually? I live in the EU, and of course, I cannot just use this tool. I’m happy to have a passive tool that tracks my portfolio and spits out the instructions to me for example: “sell 10 AAPL and buy 4 AMD to balance your portfolio”. I’m more looking for education around operating such a fund, when to rebalance, when to make a stop loss limit etc. Of course, my money I cannot live without is in High yield savings account and Vanguard ETFs. I will only play with ^ ideas with the money I gamble on stock picking.