I've tried a variety of tools to get accurate 1/4" seams and Diagonal Seam Tape has been the most effective for me.  This tape is intended for diagonal seams such as for Half Square Triangles (HSTs) or Flying Geese but I use it for plain straight seams for very accurate results.

Stripology XL Ruler from Creative Grids.  Total game changer.  Cut strips and pieces in a fraction of the time.

Flying Geese Rulers

Sewline Air-Erasable Fabric Pen

Sewline Fabric Glue Pen

Heat-Resistant Plastic for Applique Templates

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I wanted to find a more affordable plastic for applique templates.  I found this at McMaster-Carr:  Moisture-Resistant Polyester Film Clear, 10 Feet Long x 0.01" Thick x 40" Wide.  Cost is about 1/3 of the often-used quilt template plastic.  There is also a 25' length where the cost is about 1/4 of the often-used quilt template plastic.