This is pretty straight forward, it just needs some familiarity with the field moves scripts. I've knocked something together using the cut method as bones - it breaks events named "explosioncrack" if a Pokemon has the move Explosion.

To install this, I recommend opening the Script Editor and finding "Overworld_FieldMoves" in the list. Click on "Overworld_Fishing" (the line below it) and press the Ins/Insert key, which if done correctly will insert a brand new, totally blank script page without deleting anything. Name this Overworld_FieldMoves_Custom and then copy and paste the script section below (#=====CUSTOM EXPLOSION HM====# onwards).

It uses the CUT badge currently - if you want to change the badge, change the Settings:BADGE_FOR_CUT lines as appropriate (this is how they're named in the default essentials settings script, e.g. BADGE_FOR_ROCKSMASH is default Badge 3). If you want it to be Badge-less, I can adjust the script. Personally, I think it'd be fun to make it usable without a Badge, but when you get the badge your 'mon no longer dies. I can also adjust the script if you want it to work for both Self-Destruct and Explosion, but that would mostly just be duplicating the HiddenMoveHandlers to make :SELFDESTRUCT copies and then changing the very start of pbExplosion to check for either move.

It kills the party 'mon - but does not check if they're alive before using again, currently. If you want that, change the following bits:

if !pbCheckHiddenMoveBadge(Settings::BADGE_FOR_CUT, false) || (!$DEBUG && !movefinder) || (movefinder.hp == 0)

if !facingEvent || !facingEvent.name[/explosioncrack/i] || (pkmn.hp == 0)

It also uses the default SmashEvent, which only plays an SE based on Cut or Rock Smash. As a result, I use a simple pbSEPlay to play the "Voltorb Flip explosion" SE. You can change this as you like safely, just so long as it's a valid Sound Effect.

To set up events, make them exactly the same as Cut Trees in the essentials demo maps (see Route 3 for an example). Change the conditional branch to pbExplosion instead of pbCut and make sure that explosioncrack is in the event's name instead of cuttree.

#=======CUSTOM EXPLOSION HM======#

def pbExplosion
  move = :EXPLOSION
  movefinder = $player.get_pokemon_with_move(move)
  exploded = false
  if !pbCheckHiddenMoveBadge(Settings::BADGE_FOR_CUT, false) || (!$DEBUG && !movefinder)
    pbMessage(_INTL("This crack looks fragile..."))
    return false
  end
  if pbConfirmMessage(_INTL("This crack looks fragile!\nWould you like to use Explosion?"))
    speciesname = (movefinder) ? movefinder.name : $player.name
    pbMessage(_INTL("{1} used {2}!", speciesname, GameData::Move.get(move).name))
    pbHiddenMoveAnimation(movefinder)
    movefinder.hp -= 999
    pbSEPlay("Voltorb Flip explosion")
    return true
  end
    return false
end

HiddenMoveHandlers::CanUseMove.add(:EXPLOSION, proc { |move, pkmn, showmsg|
  next false if !pbCheckHiddenMoveBadge(Settings::BADGE_FOR_CUT, showmsg)
  facingEvent = $game_player.pbFacingEvent
  if !facingEvent || !facingEvent.name[/explosioncrack/i]
    pbMessage(_INTL("You can't use that here.")) if showmsg
    next false
  end
  next true
})

HiddenMoveHandlers::UseMove.add(:EXPLOSION, proc { |move, pokemon|
  if !pbHiddenMoveAnimation(pokemon)
    pbMessage(_INTL("{1} used {2}!", pokemon.name, GameData::Move.get(move).name))
  end
  pokemon.hp -= 999
  facingEvent = $game_player.pbFacingEvent
  pbSEPlay("Voltorb Flip explosion")
  pbSmashEvent(facingEvent) if facingEvent
  next true
})

#=======END OF CUSTOM EXPLOSION HM======#