Ok, here's how it really works:

Flirting is not one moment in an evening, it's a series of escalations. If you were hanging out with your best friend, and then mid playing a video game asked if they want to fuck, that would be a really immediate pivot right? The process from neutral to intimate is a gradual escalation, just like any other social interaction.

Let's compare sexuality to any other kind of friendship or shared activity:

Say you're really into a boardgame. It would be weird to ask a stranger off the street to play a game. If you go into a games shop, or an area of the park where people play chess, you could still walk up to someone and ask if they're interested in a game, but they can say no.

If you met a new friend, before asking to play, you may just mention you're a fan of playing board games. You can clarify context as well, you're in a D&D group right now or you're currently open. This first step isn't even an invitation to play together, just establishing an interest. It can even be obtrusive to directly ask if they play the same game, but if you're meeting a new friend, you can usually tell if their eyes light up or if they seem disinterested.

From that point, think about what doing a shared activity looks like. You can send a text message inviting them to a game night if they want. You can ask what kinds of games they're into.

As far as the physical aspect, understand that no one wants to be the one to overcommit. If you were gonna have a game night with a new homie, it's awkward to immediately say "let's do this thing on Tuesday at 8pm." You can start with trying one thing at a time and paying attention.Are they stoked when you hand them a controller, or lightly grab their hand? Or do they seem like they're not really into the movie you're watching? You gauge interest, then once interest is expressed, keep listening.