Hi there, and welcome to the forums.
I think your list is off to a good start, but could use a few changes. Right off the bat, you are playing three copies of Secret Box, and two copies of Deluxe Bomb. Both of these cards are ACE SPEC cards. When building your deck, it can only contain a single copy of a single ACE SPEC (in your case, only one Secret Box OR Deluxe Bomb).
Second, I've noticed you're playing a lot of Supporter cards, but not very many Items (or other trainers, for that matter). I'll have to re-read some of the supporters, but here are some things of note:
1. With how your deck currently is, Crispin does not help you. You are only playing a single type of Basic Energy (Water), so all Crispin will do is add a single Basic Energy to your hand. I would consider either removing the copies of Crispin altogether and replacing them with copies of Earthen Vessel (less ideal), or play a few different types of energy to make better use of Crispin (this will also help power up Lapras's second attack). I would also strongly consider adding a few copies of Earthen Vessel to help you get energy cards into your hand.
2. While I understand the appeal of healing your Pokemon, Cook is, unfortunately, not a very good way to do it. It only heals 70 damage from your active Pokemon, all while costing the use of your Supporter during your turn. Additionally, in a lot of cases, healing 70 damage is not going to be very impactful.
3. You are only playing two copies of Kofu. If you intend to use the Crabominable, you should be playing four copies of Kofu. However, if your intention is to use Lapras and Greninja, I would outright remove the Crabominable/Kofu copies altogether.
4. Lana's Aid is ok, but you may want to consider replacing 1-2 copies of Lana with Night Stretcher from Shrouded Fable. Same general effect, but as an item.
5. The rest of the supporters are fine, but there are better supporters to play (Iono and Arven are pretty important right now). I'll leave things be for a little bit.
Here are the overall changes I would consider:
I don't know what ACE SPEC I would play in a deck like this, so let's keep the Secret Box for now.
-2 Secret Box
-2 Deluxe Bomb
Let's remove all copies of Cook, Kofu, and the Crab evolution line.
-2 Cook
-2 Kofu
-2 Crabominable
-2 Crabrawler
Let's remove one copy of Lana's Aid.
-1 Lana's Aid
That leaves us with 13 open slots in the deck to fill. Let's start by adding another Lapras. This will help make sure you have enough copies, and don't have to worry about one ending up in your prize cards.
+1 Lapras ex
Let's add a fourth copy of Crispin, and some different types of Basic Energy to make Lapras more useful.
+1 Crispin
+3 Metal Energy
+3 Psychic Energy
Now we have way too much Energy. Let's remove some to balance things out.
-6 Water Energy (leaves us with 8 Water)
-2 Double Turbo Energy (doesn't really help Lapras or Greninja).
We're still at 13 slots left, but now have a bit more Energy to work with. Let's make it so we can find our Energy Cards.
+2 Earthen Vessel
Down to 11 slots left. Let's change up some of our Pokemon a bit, and add a few more. The Froslass from Twilight Masquerade is a lot stronger than the Glalie. You aren't playing many Pokemon with abilities, so the Froslass will help you more than the Glalie.
-2 Glalie
+2 Snover
+4 Frosslass
Down to 7 slots left. Let's add a few more ways to add Pokemon to your hand.
+3 Ultra Ball
+1 Hisuian Heavy Ball
Down to 3 slots left. Let's add a little more consistency, and some ways to help get Greninja out faster.
+1 Radiant Greninja
+2 Technical Machine: Evolution.
That should put us at 60 cards. You deck would look like this:
Pokemon: 21
3x Lapras ex
3x Greninja ex (Stellar Crown)
3x Frogadier
3x Froakie
4x Froslass (Twilight Masquerade)
4x Snorunt
1x Radiant Greninja
Energy: 14
8x Basic Water Energy
3x Basic Psychic Energy
3x Basic Metal Energy
Trainers: 25
1x Area Zero Underdepths
4x Crispin
1x Lacey
2x Carmine
1x Kieran
1x Lana's Aid
2x Earthen Vessel
3x Ultra Ball
1x Hisuian Heavy Ball
4x Nest Ball
2x Super Rod
1x Secret Box
2x Technical Machine: Evolution
Total: 60
Just a quick disclaimer: this isn't going to be the strongest deck ever, but will likey feel more consistent than the list you provided. There are absolutely better cards that can be played. I assume you are largely trying to work with cards you have on hand, so I didn't want to change the list too radically. Others might chime in and have better suggestions than I have.
Thanks, and enjoy your time here at Pokebeach.
