first off, set your render distance to 3 or 4 (depending on how fast your pc can load chunks), there's more bedrock to see at 4 but 3 will make you load in faster

now when you spawn in, drop down and break one of these blocks or any other block that will leave you with a 2x1 wall in front of you when you go in the hole (as long as it's a dirt block, since you will need to place the dirt later)

once you've broken the block, go in the hole created, look at the block directly in front of your head (like this ) and spam 3, to get the dirt in your hand as fast as possible

now for the clip. since you don't actually have to reach bedrock, we'll be doing a clip that doesn't actually bring you through the ground, but just lets you see through it to reach bedrock. to do this, place the dirt block where you're looking, and it should make your head go inside the block. now, look down as fast as possible, to see the bedrock before you clip back out

that's it, you probably didn't see any bedrock, what you need to do now, if you think you got a good time, is upload it to youtube (I usually do unlisted) and search through the frames with , and . till you see the first frame where you can see bedrock. if you want to get the exact time, then you can use yt frame timer or SPRT, but I usually only do that if the timer is green on the frame I see bedrock, when comparing to pb or wr.