Setup autoboot menuhax, through browserhax.
Steps:
1. Put the contents of starter folder from the starter.zip (
http://smealum.github.io/ninjhax2/starter.zip) onto the root of your SD Card.
2. Change your theme 2-3 times, from default stock one to any other, and finally back to default stock one.
3. Open the browser, then open the browser settings as fast as possible, scroll to the bottom and Initialize Savedata or Clear All Save Data, as fast as possible.
4. Navigate to
http://yls8.mtheall.com/3dsbrowserhax_auto.php (Keep trying until it works)
5. Open the menuhax_manager app.
6. Press A to install. Just look for a success message towards the end to know it was successful, disregard any errors messages that may appear prior to the success message.
7. Go back to the main menu of menuhax_manager, and go to then select "Configure/check haxx trigger", Press A to continue, then select "Type1" or "Type2"
If I remember correctly, both type 1 and type 2 can work as autoboot.:
For type 1) Don't hold any buttons and touch the bottom-screen for autoboot menuhax. (Pressing any other button from cold boot should cancel autoboot)
For type 2) Hold the desired button you want to cancel autboot menuhax at col boot, and while holding it touch the bottom-screen. (This means holding this button will actually cancel autoboot)
8. Depending on you configured your haxx trigger, will depend on how menuhax launches and behaves from now on autoboot, it'll load the boot.3dsx on the root of your SD Card, which should be Homebrew Launcher by default.
Consider using CTRBootManager and setting it to autoboot ReiNAND:
Link:
https://gbatemp.net/threads/ctrbootmanager-3ds-boot-manager-loader-homemenuhax.398383/
You still need internet to get menuhax installed properly the first time around, but after that you don't. Also, menuhax does have a failure rate of launching properly, consider A9LH if you must have 100% bootrate, but it's a pretty long guide and can take a while to setup properly, ask questions if you need help.
A9LH Guide:
https://github.com/Plailect/Guide/wiki
There is also this to improve menuhax bootrates:
http://gbatemp.net/threads/guide-how-to-improve-menuhax-boot-rate-to-nearly-100.410764/
You could also look into lesshax as opposed to the solution above.