Is there an official or generally accepted method for allowing players to create a spell? I know the DMG offers tips on how a DM could create a new spell. But nothing specific on how a player could actually go about doing it.
I have been brainstorming ways to allow my players to do it, but there are a lot of variables at play when you are getting into spell levels, damage, etc. It gets pretty complicated and convoluted pretty quick, which is probably why I cant find anything in the official rules.
I'd say that you're going to want to treat it almost like crafting a magical item... the characters would need to spend time researching, and probably making arcana checks through out to make sure they're successful. There would have to be material components purchased and consumed in the process... you could justify that in experimentation they might consume more expensive components than the finished spell actually requires through experimenting (like, if the finished spell has a component requirement of a pearl costing at least 250 gp, research might consume 2,500gp worth of pearls through experimentation).
I've had players in my game craft spells before. I didn't use any official ways to do so. I figured Tasha's Hideous Laughter and Melf's Acid Arrow were cool concepts that I had my players create a spells, such as "Marcell's Red Tide" and "Hallice's Smooth Hands". Each of them had to do with the character's backstory and the question posed was, why did your character craft this spell, and how did they craft it. Once they had that, it was just a matter of finding out which level spell it should be, which I'm terrible with. I posted the spell on the forums and got some other insight to make sure that the spells weren't overpowered for the level, or underpowered. These forums are a great place for 2nd and 3rd opinions!
Yeah, same with the others said. I actually play a wizard who does this too, and both myself and DM have used a method of resource and time spent to make the spells.... though we do use the crafting a spell scroll as a base, we also kinda combined it with the copy spells rules for wizards. That way it would be easier for my character to learn how to make spells of his school of focus while not hindering my character too much.