Tiling an Excel array in 2 dimensions, ideally not using VBA

I'm looking to tile an Excel array in 2 dimensions, as defined by another array, ideally not using VBA.

To explain better, what I would like is an excel formula for f(A, B)

Where A is boolean and =

[[1, 0],
 [0, 1]

Where B =

[[1, 2],
 [3, 4]

And f(A, B) tiles B according to bool values in A, in this case, f(A, B) =

[[1, 2, 0, 0],
 [3, 4, 0, 0],
 [0, 0, 1, 2],
 [0, 0, 3, 4]]

My initial thoughts were of =IF(MUNIT(2), {1, 2;3, 4}, {0, 0;0, 0}) but the output does not expand well.

This is my effort so far - hopefully it's fairly general:

=LET(A,A1:B2,B,D1:E2,DROP(REDUCE(SEQUENCE(1,COLUMNS(A)*COLUMNS(B)),SEQUENCE(ROWS(A)),LAMBDA(rowAcc,row,VSTACK(rowAcc,
   DROP(REDUCE(SEQUENCE(ROWS(B)),SEQUENCE(1,COLUMNS(A)),LAMBDA(colAcc,col,HSTACK(colAcc,B*INDEX(A,row,col)))),,1)))),1))

You could also use Makearray:

=LET(A,A1:B2,B,D1:E2,rA,ROWS(A),rB,ROWS(B),cA,COLUMNS(A),cB,COLUMNS(B),
MAKEARRAY(rA*rB,cA*cB,LAMBDA(r,c,INDEX(A,(r-1)/rB+1,(c-1)/cB+1)*INDEX(B,MOD(r-1,rB)+1,MOD(c-1,cB)+1))))

(Same logic as @Scott Craner's legacy version)

Here is some sample VBA code in case you wanted to go down that route:

Sub Kron()
    Dim AR As Range, BR As Range, OutR As Range
    
    ' A is the boolean array, B is array to be tiled.
    
    Dim A() As Variant
    Dim B() As Variant
    
    Dim aRows As Long, bRows As Long, aCols As Long, bCols As Long, outRows As Long, OutCols As Long
    
    Dim aRow As Long, aCol As Long, bRow As Long, bCol As Long, outRow As Long, outCol As Long
    
    Dim Out() As Integer
    
    Set AR = Range("A1:C2")
    Set BR = Range("D1:F3")
    Set OutR = Range("Q1")
    
    A = AR.Value
    B = BR.Value
    
    aRows = UBound(A, 1)
    aCols = UBound(A, 2)
    
    bRows = UBound(B, 1)
    bCols = UBound(B, 2)
    
    
    outRows = aRows * bRows
    OutCols = aCols * bCols
    
    ReDim Out(outRows, OutCols)
    
    ' Loop over boolean array A
    
    outRow = 1
    For aRow = 1 To aRows
        outCol = 1
        For aCol = 1 To aCols
        
            ' Only call Tile if A contains 1
            
            If A(aRow, aCol) = 1 Then Call Tile(Out, B, outRow, outCol, bRows, bCols)
            
            outCol = outCol + bCols
        Next aCol
        outRow = outRow + bRows
    Next aRow
          
    OutR.Resize(outRows, OutCols) = Out
     
End Sub

Private Sub Tile(Out, T, startRow, startCol, height, width)
    Dim tileRow As Long
    Dim tileCol As Long
    Dim outRow As Long
    Dim outCol As Long
    
    'Loop over tiling array locally called T
    
    outRow = startRow
    For tileRow = 1 To height
        outCol = startCol
        For tileCol = 1 To width
            Out(outRow, outCol) = T(tileRow, tileCol)
            outCol = outCol + 1
        Next tileCol
        outRow = outRow + 1
    Next tileRow
End Sub