Lynna Village
Past
1. You can dig out a Heart Container Piece in front of the Black Tower after you've gotten the shovel.
Maku Road
2. Push either block closer to the wall inward and the one next to it off to the side to reach a trapped Heart Container Piece along the way to the Maku Tree.

Lynna City
Present
1. In the past, go one screen right from the statue in the water. Stand at the top left corner of the tree near the top of the screen and travel through time. If all goes well, you'll have access to a fenced-off shop. A Heart Container Piece is for sale inside for 500 Rupees.

Yoll Graveyard
Present
1. Lift a rock west of the Spirit's Grave once you have the Power Bracelet.

Deku Forest
Past
1. Burn a small tree in the southwestern corner of the forest to uncover a hidden staircase.

Restoration Wall
Past
1. Inside a small cave near the base of the right side of the wall.

Talus Peaks
Present
1. Travel through time from the past to reach a Heart Container Piece trapped at the very top left corner of the mountain.

Rolling Ridge
Present
1. Go to the very top right corner of the map in the past. Chop down a few of the bushes on the right and travel to the present to reach a Heart Container Piece.
Goron Cave
1. Enter the cave in front of where the tree grows Pegasus Seeds in the past (the very west side). Blow a hole in the east wall in front of the Goron.

Crescent Island
Present
1. Once you have the Mermaid Suit, dive under the island to find an underwater maze. Make your way to the cave to find a Heart Container Piece.

1. Maple will drop a Piece of Heart at Random, so run into her as often as possible.
2. Eventually, you will get a Piece of Heart from a Gasha Nut.