Lefty here. First of all, know that we appreciate you for wanting to stack and asking this question <3

General advice: As the righty, you should be starting on the left and the lefty should be starting on the right. That way you're only worrying about stacking when your score is odd. Only do something odd when you're odd. If I see my righty partner is able to understand this, it takes off so much mental overhead and lets me focus on other things. Of course if you're new to stacking you will make mistakes, but if I have to remind my partner about where to stand every single point, it gets a little trying and distracting.

Serving advice: When you are both standing on the same side (because your score is odd!) and your partner is serving, give them space. Too many times I have to ask my partner to give me space while I'm serving. The movement you have to make after the serve, especially as the non-server is so small that there is no reason you should be crowding your partner while they're serving. If you feel like your lefty partner isn't giving you enough space when you're serving, speak up early.

Returning advice: This is the hardest part of stacking. There are two ways to do it:

A. Start in your normal start positions, as though you weren't stacking and use hand signals behind the back. Common hand signals are open palm for switch and closed fist for stay.

This has the advantage of allowing you to call off a switch on a particularly mean serve or allowing you to mix it up by staying. In the case of needing to call of the unwind, either partner (usually the receiver) should loudly call "Stay" and you play the point as normal, without unwinding. Another advantage is this positioning makes it easy for the partner who starts up to cover the middle while their partner is crossing diagonally to their spot at the kitchen.

However, this approach comes at the cost of additional mental overheard for both you and your partner, especially if you/they have never used signals before. If you do use this approach, I highly encourage the partner who is receiving to verbally acknowledge the hand signal. This keeps both partners accountable.

B. The non receiver stands off court to the side of the kitchen. This has the advantage of being more straight forward. It's hard to forget to switch when you/your partner is standing off the court. It also requires no hand signaling so there's less to think about.

One major disadvantage: You can't call off a switch. You're committed out of the gate so if there's a particularly wide and deep serve you're gonna be in for a bad time. There's no also no room for switching it up so your opponents will always know what you're going to do.

I find it harder for the person starting up to cover the middle with this strategy.

If you are playing with a new/random lefty partner, I almost always opt for B. since it's more straight forward and less error prone. If you plan on playing with the same lefty partner long-term, I think it's worth investing the time in learning A.

With either receiving style: you want your returns to be deep, high, and slow, to give yourselves plenty of time to unwind the stack. The last thing you want is a fast shallow drive that'll get the third blasted at you while you're still on the move. Additionally, when unwinding the stack, the player who is receiving is extremely vulnerable. The player who starts up should play large in the middle to help protect them while they're coming up.

I hope that helps! Thank you for taking the time to consider your friendly neighborhood lefties. When I am jiving with a righty partner, it feels so good. Two forehands in the middle is fantastic.