I've written about one shots before, and one of my tips for a successful quick game of D&D is to bring prebuild characters. However, there are two potential problems with that advice:
Somebody needs to build those characters
A player may want to build their own character just for the experience or out of preference
I've gotten the 5e character build process down to just under 12 minutes. It's not a complete build and it wouldn't be suitable for a long campaign, but for a single game session, such as you might play at a conference or at a friend's house after dinner, it's perfectly usable. Additionally, you can use this method to build a character at any level.
The theory behind the 12-minute build is that much of the power scaling in 5e is attributable to the proficiency bonus, and that the primary mechanic in a quick game is the d20 roll. Sure, each class has special features that get introduced along the way to help characters gain power, but in a one-shot game those features are secondary to the real workhorse of D&D 5e: rolling a d20 and adding your attribute modifier and proficiency bonus.
You can use this method to build a few characters before your friends arrive for an evening game, or you can use it to guide your friends while they build their own characters at the table.
Keen to give it a try? Here it is. Feel free to time this.
Pick a class and use the Quick Build section to dictate what features and spells you take. Write those features on a sheet of paper or character sheet.
Skip choosing a background, you don't have time for that.
Write down the features listed under Class Features, including Hit Dice, Hit Points (use the average), Proficiencies, and Equipment.
Pick 5 Skill proficiencies (3 standard plus 2 for having skipped over background selection.)
Use the standard array (15,14,13,12,10,8) to assign scores to attributes. Boost one score by 2 for free (you're using Tasha's Cauldron rules for a custom lineage.)
Your speed is 30 feet.
Add your CON modifier to HP.
Your AC is 10 + DEX modifier.
Choose your level.
Multiply your HP and your Hit Dice by your level to determine their new values.
Record the data in the class table. This includes your level, proficiency bonus, features, and spell slots for magic users.
If you're building a character with spell slots above level 1, then you will upcast the existing spells you gained at level 1.
Choose a race and a name.
12 minutes, almost guaranteed.
It's not perfect, but it's only 12 minutes. There's plenty of room for experienced players who are familiar with their class to choose a feat or to use one of their class abilities that this build skips over. You can make an allowance for a new player to leaf through the PHB for an interesting spell while another player is taking their turn in combat. The idea, though, is to get everyone at the table a playable character in the minimum amount of time, and for that playable character to feel like a D&D character. Using a little bit of PHB quick build tips and a little bit of Tasha's customization, this gets pretty close, especially at low levels.
And any way, it's a one shot. By the time anyone thinks to complain that they don't have enough cool stuff to do, they'll have already slaughtered three demons and looted a room full of magic items. Don't sweat the build.
Header image of Icewind Dale character sheets by Wizards of the Coast