Here is how Flas Sentry proposes to Twilight Sparkle in The Magic of Friendship.
That night, Jiminy Cricket and the Mane 6 are hanging out in The Friendship Rainbow Kingdom after meeting the rest in Ponyville.
Trixie: Alright, Jiminy Cricket, Witness the magic spell developed by us, The Great and Powerful Princess Trixie and Sunset Shimmer, For we are the apprentices of Princess Twilight Sparkle.
Sunset Shimmer: Here it goes. (as she and Trixie began their spell to make a Crystal Ball from the Forcefield)
The Mane 6 and Spike: (cheered)
Twilight Sparkle: So, Jiminy, What do you think of Ponyville?
Jiminy Cricket: Well, I think it's swell, Twilight, You're very lucky to be a Princess and have great friends.
Twilight Sparkle: Well, Back then I was a Unicorn when I learned magic from my mentor, Princess Celestia, Then I got wings and became an Alicorn.
Jiminy Cricket: That's unbelievable, Twilight. Later, Discord appeared out of nowhere.
Discord: Excuse me for interrupting, Twilight, But you got a visitor.
Twilight Sparkle: Okay, Thanks, Discord.
Discord: And you must be Jiminy Cricket, The Official Conscience.
Jiminy Cricket: How do you know who I am?
Discord: Fluttershy told me a lot about you.
Then, Flash Sentry arrived.
Flash Sentry: Hey, Twilight!
Twilight Sparkle: Hey, Flash, What brings you here?
Flash Sentry: Just wanted to let you know that Princess Celestia and Princess Luna are holding a Banquet for you in Canterlot, Your friends are invited and your Brother and Princess Cadance are on their way right now.
Twilight Sparkle: That sounds wonderful, What do you say, girls, Shall we go to Canterlot?
Applejack: Count on me.
Rairy: That's a grand idea.
Pinkie Pie: That'll be great!
Fluttershy: Oh my, we better get ourselves ready.
Rainbow Dash: This is gonna be awesome!
Spike: I can't wait.
Discord: Well, What are you waiting for?
Then, Sunset and Trixie found something.
Sunset Shimmer: Trixie, Look!
Trixie: It's a Treasure Map, I think I know just the one who's up for this Task, Twilight told me all about her.
Later, At Canterlot.
Princess Celestia: We bid you Welcome to Canterlot, Jiminy Cricket!
Princess Luna: We hope you find this a Welcoming committee.
Jiminy Cricket: I sure do, Your Majesties.
Meanwhile with Flash and Twilight at the Balcony after the song Love.
Twilight Sparkle: The stars are beautiful tonight.
Flash Sentry: Yeah, They sure are.
Twilight Sparkle: So, Flash, Is there something you want to tell me?
Flash Sentry: Hmm? Oh, Yes, (clearing his throat) Twilight Sparkle, You mean everything to me in life ever since we've first met, Now that we're alone, There's something I wanted to ask you for a long time.
Twilight Sparkle: What is it?
Flash Sentry: (showing Twilight the ring) Princess Twilight Sparkle, Will you marry me?
Twilight Sparkle: It's beautiful, (staring at the ring) Yes, I will merry you, Flash Sentry!
Later, Shining Armor and Princess Cadance arrived.
Twilight Sparkle: Shining Armor! Cadance!
Shining Armor: Twily! (hugging her sister) Great to see ya, Sis!
Princess Cadance: Who's this?
Twilight Sparkle: This is Jiminy Cricket, He's our guest in Canterlot.
Jiminy Cricket: Please to meet you and your wife, Prince Shining Armor, Your sister has told me a lot about you.
Shining Armor: Pleasure's all ours.
Jiminy Cricket: (noticing Cadance's pregnant belly) Golly, You two must have been busy.
Princess Cadance: Yes, We're going to have a Baby soon.
Jiminy Cricket: Then that means...
Twilight Sparkle: That's right, Jiminy, I'm going to be an aunt and Spike's going to be an uncle.
Spike: Uncle? Me?
Princess Cadance: Well, You are after all like a little brother to Shining Armor and Twilight, Spike.
Spike: Point taken.
Jiminy Cricket: When will the baby be due?
Shining Armor: In a couple of weeks or so, Won't be long now after ten months.
Flash Sentry: Your Majesties, Permission to speak?
Princess Cadance: Permission granted, Flash, Something on your mind?
Flash Sentry: I've made a proposal to Princess Twilight to seek her hoof in marriage, Whatever your choice is to give your royal blessing to us, I'd be glad to fallow when.
Shining Armor: Flash Sentry, You've been one of my best royal guards of the Crystal Empire, Therefor You and my sister have known each other for a very long time, You two deserve our blessing.
Twilight Sparkle: (hugging her brother) Oh, Thank you, Shining Armor, Thank you so much!
Shining Armor: Anything for you, Twily.
Later, Princess Celestia give her Speech.
Princess Celestia: My faithful subjects, I would like to make an announcement, As many of you know I would like to give a pleasant welcome to our new friend, Jiminy Cricket, Also, My Proud and most Faithful Student, Princess Twilight Sparkle and Prince Shining Armor and Princess Cadance's most trusted royal guard, Flash Sentry are officially engaged, We shall now have a banquet in their honor!
Jiminy Cricket: I sure am happy for Twilight.
Spike: Me too, Jiminy.
Then, Sunset and Trixie magically appeared out of nowhere with Daring Do with them.
Sunset Shimmer: Everypony!
Flash Sentry: It's Sunset Shimmer and Princess Trixie!
Daring Do: It's an emergency!
Rainbow Dash: (gasp) Ohmygoshohmygoshohmygoshohmygoshohmygosh! Daring Do is here too!
Trixie: Princess Celestia, Princess Luna, We need your help!
Princess Celestia: What is it?
Sunset Shimmer: We found this! (showing the treasure map)
Princess Celestia: A map of the Island of Pangea that leads to the ultimate treasures!
Princess Luna: We must call this meeting at once!