What is an efficient approach to remove many cloned instances in a Workspace?

Hello, I am developing a basic flat-terrain generator, where bricks are generated over a square area with multiple layers. The problem is, there are factors that are keeping me from achieving this.

The following is my code; I will go by line references if needed since many of the commands are interconnected throughout the whole script, and the script itself is large. I wasn't sure how to auto-indent in a block formation as well, excuse me for that.

while true do

--create a group called "DirtBlockCloneGroup"
dirtBlockCloneModel= Instance.new("Model",game.Workspace)
dirtBlockCloneModel.Name= "DirtBlockCloneGroup"

local cloneBrickCount= 0
for timer= 1,0,-1 do --timer that counts from 3/ any # to 0 by seconds
    wait(1)
    print(timer)

    if timer== 0 then
    print("Done.")--ends timer, then does action below

x0= game.Workspace.DirtBlock.Position.X
y0= game.Workspace.DirtBlock.Position.Y
z0= game.Workspace.DirtBlock.Position.Z
--sets whatever position the original dirt block is in, stores ion variables
local original= Vector3.new(x0,y0,z0)

local zIncr= 3 --increments new clone blocks by changing z coordinate
--line below checks and gets testing plate size
local zSizeBase= game.Workspace.BasePlate.Size.Z
local zSizeCheck= 3--baseplate comparison, so clone won't pass plate boundaries

local xSizeBase= game.Workspace.BasePlate.Size.Z
local xSizeCheck= 3
local xIncr= 3

    for i= 1,4 do--sets how many layers of bricks
        for i= 1,(xSizeBase/3) do-- because it increments by 3 studs
            while zSizeCheck<zSizeBase do
                clone= game.Workspace.DirtBlock:Clone()-- creates clone
                clone.Name= "DirtBlockClone" -- changes name of dirt block
                clone.Parent= game.Workspace.DirtBlockCloneGroup --adds the instance into the Workspace
                clone.Position= Vector3.new(x0,y0,z0-zIncr)

                cloneBrickCount= cloneBrickCount+1

                zIncr= zIncr+3-- ex. 3 away from original, 6 away, 9 away etc.
                zSizeCheck= zSizeCheck+3

            end
        zSizeCheck= 0--these scripts reset the position, so it won't shift
        zIncr= 0
        x0= x0+3
        wait(0.001)--delay to minimize lag, edit between dev and release
        end
    y0= y0+3-- goes to the next level, 3 studs up
    x0= game.Workspace.DirtBlock.Position.X-- resets at original point
    end

    end--end of if for timer

end--end of for at very beginning
    print(cloneBrickCount)

--wait(1)-- no change
--for i=1,50000 do

--this period is the playing time before the map resets

--allow player to play buy freeing them from spawn area
game.Workspace.SpawnArea.SpawnBaseBottom.CanCollide= false
game.Workspace.SpawnArea.SpawnBaseBottom.Transparency= 1

--ex. for GUI, "Map resets in: ...

    for timeToReset= 5,0,-1 do
        wait(1)
        test2= Instance.new("Hint",game.Workspace)
        test2.Text= "Time left until map reset: "..tostring(timeToReset)
    end--end for

--players go back when map is regenerating
game.Workspace.SpawnArea.SpawnBaseBottom.CanCollide= true
game.Workspace.SpawnArea.SpawnBaseBottom.Transparency= 0.75

target= CFrame.new(60.5,3358,84.5)
for i, player in ipairs(game.Players:GetChildren()) do
    if player.Character and player.Character:FindFirstChild("Torso") then
        player.Character.Torso.CFrame= target+ Vector3.new(i*2,0,0)
    end
end
--wait(10)

wait(1)
game.Workspace.DirtBlockCloneGroup:Destroy()
wait(1)
--[[
    --alt to the single command above
    while game.Workspace.DirtBlockCloneGroup:FindFirstChild("DirtBlockClone") do
        game.Workspace.DirtBlockCloneGroup.DirtBlockClone:Destroy()
        wait(0.001)
    end
game.Workspace.DirtBlockCloneGroup:Destroy()
--]]

--[[
    --old code
for i=1,cloneBrickCount do--the exact amount of clones needed to be wrecked
game.Workspace.DirtBlockCloneGroup.DirtBlockClone:Destroy()
--111,555 bricks: =22,311*5
--wait(0.001)--edit between dev and release
end 

--]]

end--loop entire script

My first attempt was to count how many blocks were in the Workspace, which is, local cloneBrickCount= 0. Next, a for-loop was used to destroy every existing cloned brick:

for i=1,cloneBrickCount do--the exact amount of clones needed to be wrecked
game.Workspace.DirtBlockCloneGroup.DirtBlockClone:Destroy()
--111,555 bricks: =22,311*5
--wait(0.001)--edit between dev and release
end 

The problem is that there can be a variable number of bricks at each run between each map regeneration sequence. Too little of a value and not all the clones would be removed from the Workspace. Too much and the game will spawn an error saying that the brick does not exist.

My second attempt was to use a while-loop with a wait time:

while game.Workspace.DirtBlockCloneGroup:FindFirstChild("DirtBlockClone") do
        game.Workspace.DirtBlockCloneGroup.DirtBlockClone:Destroy()
        wait(0.001)
    end

The problem here is that the destroy method deletes a brick one at a time, and even with the wait time involved, it would take much longer to remove the clones efficiently than to rebuild the map (regeneration builds cloned bricks by the rows).

My latest attempt was to simply delete the model containing all the bricks (as shown in the code), but that can cause massive lag and possibly a server crash. The upside is that it is very fast.

The only other idea I had in mind was to us smaller wait times such as wait(0.0000000000001) if that makes a difference.