Genuine question, how could I actually make the proposal of a harem RP appealing?

I understand the prospect of asking for a harem RP may seem a little selfish. I cannot lie, it’s the ERPs I enjoy the most.

I’ve been on the other end of making one many time before but I enjoy when I get to play into a world I can explore and create different relationship with various challenges.

I love creating characters that comes with depth overtime. I build their backstories, personalities and flaws along side the story I build with a partner. I’m not the one dude who’s going to play “Steve” and Steve has the personality of a cardboard box.

So How can I make it seem like I’m more than that when I post an ad? How can I show I’m being serious and I’ll make the effort and this may seem appealing for my partner?

Because I feel like it’s hard to do so unless someone decides to actually give me a chance to put in the effort.

Edit: When I’m asking about this question, I’m asking on how to propose of being the one person who’s the harem owner, not the other way around. I have already done posts proposing to be the harem and those works out easily, it’s already appealing as it is.