So I've thought about this for a while now. And I've allowed my wizard to roll a sleight of hands check contested by their perception check to cast a spell with all components involved.
But if you have to smack bat shit and sulfur together, throw it where you want and then say "Hocus pocus mother****er!" In a weird ancient tongue... It's gonna be harder.
So I wanted to hear if it's just when you need 1 component you can do this or....? Because Bat shit and sulfur is hard to stealthly smack together. While grabbing a crystal around your neck is easier but still a little fishy. Verbal I thought you had to speak in a specific tongue but of course not.. but it feels a little off to me that the verbal component could be:
"Man.. **** me!". So to make a long... so to cut this short... What is the best way to do this. As I wanna allow it and the sorcerer I have in another group gets meta magic and can cast subtle spell which I would just say that unless people have a passive perception equal to or higher than your spell save DC then they don't notice. Thanks in advance! ^^

-Daergiel

Your username does not seem accurate.

But anyway, it's just like you say. The subtle spell metamagic allows the caster to cast without verbal or somatic components. That's the whole point of it. That doesn't necessarily mean others don't notice they are still casting. It just means they can cast while tied up or restrained or gagged or within the radius of a silence spell or whatnot.

EDIT: Looks like I need to revise my answer. Subtle spell does specifically avoid people perceiving the caster casting the spell so no perception check would apply, nor would a sleight of hand or deception check be required. But if someone sees you standing there and suddenly a bolt of flame shoots out, they are obviously going to know who it came from even if they notice too late to do anything about it.

Most of the components are deliberately non-specific so a DM can rule how they like. But they are movements, noises, and objects that together affect the weave to produce a magical effect, and I would think they do not look or sound natural. 

For clerics, paladins, and warlocks, I've thought of the verbal component to be more of a prayer: "Oh dark master, grant your servant the power to drive out the light. Darkness"

Wizards, sorcerers, and bards use more arcane sounds "abra kadabra"

Either way, I enforce the rule of "Spell voice" the sort of echo you here on TV spell. Anyone who can hear you can tell you are casting a spell.

But that is just me, the rules don't really state that you have to do this.

Thank you for this! I think it would be something like this:

All Components: Sleight of Hand vs Perception Check
2 out of 3 Components: Sleight of hand with advantage (or no check if it's explained in a reasonable way by the PC)
1 out of 3 Components: Passive Perception vs Spell Save DC

Thank you both for you help though! ^^

A lot of the material component details are a legacy of 1st edition where a round was one minute long. Things that made sense with a one minute round can seem physically impossible with a 6 second round. I wouldn’t sweat the details. If a spell can be cast as 1 action then somehow you can do that in a few seconds and walk 30’ and ...

I use the spell descriptions as a guide to how obvious casting a particular spell would be, and also consider the context in which that spell was designed to be used. For example, charm person is clearly meant to be used in short-lived social encounters (convincing a guard to let you pass, etc.). It has just verbal and somatic components. To me, that gives the impression that casting charm person looks similar to a Jedi using the Mind Trick - a subtle hand gesture and some wording that may seem a bit off but could be passed off as normal conversation.

Chaos bolt, on the other hand, is very clearly a combat spell. It results in an "undulating, warbling mass of chaotic energy." Even though it also requires only verbal and somatic components, given the way the spell description is written, and given its intended use, I imagine its verbal/somatic components are much bigger, more dramatic, and not something you could pass off in normal conversation unless you had the subtle spell metamagic.

Obviously you're free to house rule this however you want, but I wouldn't even allow sleight of hand checks. Either cast the spell according to its requirements or don't cast the spell. Letting someone back-door into subtle spellcasting through sleight of hand checks cuts into the value of that sorcerer metamagic ability. If you want to cast spells subtly, play a sorcerer and pick up subtle spell metamagic.

That I'm doing too yeah. I agree with that, as some spells like disintegrate could be used both in and out of combat so depending on the situation you could modifier the rule.
thank you for the input man! ^^

-Daergiel